campoy / justforfunc

The repository for the YouTube series JustForFunc

justforfunc

Hello, there!

This repository contains the code for most of the episodes from the YouTube series #justforfunc.

Episodes

• 0: Hello, World! (video)
• 1: A Code Review (video and source code)
• 2: The Magic Gate (video and source code)
• 3: The Magic Gate (part 2) (video and source code)
• 4: Code Review for a Twitter Client (video and source code)
• 5: Defining a Color Flag in Go (video and source code)
• 6: Flappy Gopher I (video and source code)
• 7: Flappy Gopher II - Handling Events (video and source code)
• 8: Flappy Gopher III - Collision Detection (video and source code)
• 9: The Context Package (video and source code)
• 10: Implementing The Context Package (video and source code)
• 11: Review of an IRC package's API (video and source code)
• 12: A Text to Speech server with gRPC and Kubernetes (video and source code)
• 13: more Text to Speech with cgo and Docker multistage builds! (video and source code)
• 14: a twitter bot and systemd (that runs free on GCP) (video and source code)
• 15: a code review with logging, errors, and signals (video and source code)
• 16: unit testing HTTP servers (video and source code)
• 17: contributing to the Go project (video)
• 18: understanding Go's type aliases (video)
• 19: mastering io.PipesAll (video and source code)
• 20: code reviewing ursho (part 1) (video and source code)
• 21: code reviewing ursho (part 2) (video and source code)
• 22: using the Go tracer (video and source code)
• 23: plotting latency distributions with gonum (video and source code)
• 24: What's the most common identifier in the Go stdlib? (video and source code)
• 25: deeper program analysis with go/parser (video and source code)
• 26: Why are there nil channels in Go? (video and source code)
• 27: Two ways of merging N channels (video and source code)
• 28: Basic Benchmarks (video and source code)
• 29: Dependency Injection in a Code Review (video and source code)
• 30: The Basics of Protocol Buffers (video and source code)
• 31: gRPC Basic (video and source code)
• 32: CLI tools with Cobra (video and source code)
• 33: The Rise and Fall of CORBA (video)
• 34: Plotting Data with gonum/plot (ML4G #1) (video and source code)
• 35: Implementing the tree command from scratch (video and source code)
• 36: Versions, build constraints, and ldflags (video and source code)
• 37: sync.Pool from the pool (video and source code)
• 38: Linear Regression with Gradient Descent (ML4G #2) (video and source code)
• 39: code reviews are back! (video and source code)
• 40: cvsql - serving CSV with SQL (video and source code)

Have an idea?

Submit your ideas here or directly on Twitter for @francesc.

Disclaimer

This is not an official Google product (experimental or otherwise), it is just code that happens to be owned by Google.

justforfunc's Issues

Is it ok to use new context in client code?

Hi Francesc!
In your talk, you're saying that gRPC still using old context path.
But in the client code, new context path is actually used.
So my question is it ok to use new context path with gRPC?

"no such file or directory"

halfway through the video, I build the docker image through the makefile, which works,
but when i try to run docker run -p 8080:8080 campoy/say I get an error.

standard_init_linux.go:178: exec user process caused "no such file or directory"

It seems he can't find the entrypoint of the dockerfile or something.
I get this error on the latest docker version (ce).
Before I upgraded my docker version, i got almost the same error, but there, the message explicitly pointed to the "/app" that was not found.

Any suggestions?
I'm on ubuntu 16.04

Update
I Tested this with the source code of this github project itself.
Same error, Maybe an OS issue?

episode idea: cross platform library

• example of cross platform library (windows, darwin, ..., unsupported)
• best practices

34-gonum/plot: bad data points are not properly discarded

episode idea: manipulating video

I'd love to see how one would go about manipulating video with Go. For instance adding a simple text overlay to the video to show some captions.

episode 40 csvql describe

after building this out, I tried to run 'desc cities' or 'desc people' like in your part 1 video and get the error

ERROR 1105 (HY000): unknown error: unsupported syntax: &sqlparser.OtherRead{}

Timeline Plot

Greetings!

I watched the episode about Gonum, but I don't understand how to create a time-based plot ..

I need to plot it:

2020/09/11,1336.44
2020/10/20,1936.44
2020/11/01,2005.11
2020/11/01,2005.24
2020/11/25,1994.25
2020/12/04,2594.25
2020/12/04,3194.25
2020/12/14,3185.49
2020/12/21,3172.35
2020/12/22,3342.35
2020/12/22,3172.35
2020/12/30,3161.34
2020/12/31,3011.34
2021/01/01,3078.34
2021/01/20,3038.34
2021/01/22,3028.34
2021/01/25,3328.34
2021/01/25,3628.34
2021/02/01,3758.34
2021/02/02,3733.26
2021/02/16,3709.38
2021/02/16,3859.38
2021/02/16,3709.38
2021/02/22,3673.38
2021/02/24,3619.38

I'm trying:

func readData(path string) (plotter.XYs, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var xys plotter.XYs
	s := bufio.NewScanner(f)
	for s.Scan() {
		var y float64
		var x float64

		_, err := fmt.Sscanf(s.Text(), "%f,%f", &x, &y)
		if err != nil {
			log.Printf("discarding bad data point %q: %v", s.Text(), err)
			continue
		}
		s := fmt.Sprintf("%f", x)
		date1, err := time.Parse("2006/02/01", s)
		date2, _ := strconv.Atoi(date1.String())
		x = float64(date2)
		xys = append(xys, struct{ X, Y float64 }{x, y})

		if err != nil {
			fmt.Println(err)
		}

	}
	if err := s.Err(); err != nil {
		return nil, fmt.Errorf("could not scan: %v", err)
	}
	return xys, nil
}

What I'm doing wrong?

Thanks in advance!

31-grpc not working: undefined: proto.InternalMessageInfo

Hello, I am using go version go1.10.2 darwin/amd64. Building the server works with the provided code.
The example isn't working after re-generating the pg.go file using:

 protoc -I . todo.proto --go_out=plugins=grpc:.

The error:

$ go build server/main.go
# github.com/campoy/justforfunc/31-grpc/todo
../todo/todo.pb.go:56:26: undefined: proto.InternalMessageInfo
../todo/todo.pb.go:101:30: undefined: proto.InternalMessageInfo
../todo/todo.pb.go:139:26: undefined: proto.InternalMessageInfo
../todo/todo.pb.go:176:26: undefined: proto.InternalMessageInfo

I have done this for the dependencies, although it is not very clear which ones to use:

 go get -u -v github.com/golang/protobuf/proto
 go get -u -v github.com/gogo/protobuf/proto

maybe use glide for the proejects in the future in order to clarify?

Is this related to this: https://groups.google.com/forum/#!topic/golang-nuts/F5xFHTfwRnY ?
if it is, how do we move past this?
Thanks

EDIT: Here is the regenerated code

https://gist.github.com/trobert2/d8eb11ba7f1cec92241ba4d079993852

needs installing protoc

First of all Great episode (#12) about grpc, enjoyed it, just wish you had mentioned you need to install protoc it could be a lil painful to install it.

Timeline Plot

Greetings!

I watched the episode about Gonum, but I don't understand how to create a time-based plot ..

I need to plot it:

2020/09/11,1336.44
2020/10/20,1936.44
2020/11/01,2005.11
2020/11/01,2005.24
2020/11/25,1994.25
2020/12/04,2594.25
2020/12/04,3194.25
2020/12/14,3185.49
2020/12/21,3172.35
2020/12/22,3342.35
2020/12/22,3172.35
2020/12/30,3161.34
2020/12/31,3011.34
2021/01/01,3078.34
2021/01/20,3038.34
2021/01/22,3028.34
2021/01/25,3328.34
2021/01/25,3628.34
2021/02/01,3758.34
2021/02/02,3733.26
2021/02/16,3709.38
2021/02/16,3859.38
2021/02/16,3709.38
2021/02/22,3673.38
2021/02/24,3619.38

I'm trying:

package main

import (
	"bufio"
	"fmt"
	"image/color"
	"log"
	"os"
	"strconv"
	"strings"
	"time"

	"gonum.org/v1/plot"
	"gonum.org/v1/plot/plotter"
	"gonum.org/v1/plot/vg/draw"
)

func main() {
	xys, err := readData("test.txt")
	if err != nil {
		log.Fatalf("could not read data.txt: %v", err)
	}
	_ = xys

	err = plotData("out.png", xys)
	if err != nil {
		log.Fatalf("could not plot data: %v", err)
	}
}

func readData(path string) (plotter.XYs, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var xys plotter.XYs
	s := bufio.NewScanner(f)
	s.Split(bufio.ScanLines)
	var txtlines []string

	for s.Scan() {
		txtlines = append(txtlines, s.Text())
	}
	for _, eachline := range txtlines {
		lines := strings.Split(string(eachline), ",")

		var x float64
		var y float64

		t := strings.Split(lines[0], "/")

		year, _ := strconv.Atoi(t[0])
		month, _ := strconv.Atoi(t[1])
		day, _ := strconv.Atoi(t[2])

		println(year, month, day, lines[1])

		date := time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.UTC).Unix()
		x = float64(date) 
		fmt.Println(fmt.Sprintf("%f", x))

		y, err = strconv.ParseFloat(strings.TrimSpace(lines[1]), 64)
		fmt.Println(fmt.Sprintf("%f", y))

		xys = append(xys, struct{ X, Y float64 }{x, y})

		if err != nil {
			fmt.Println(err)
		}
	}
	if err := s.Err(); err != nil {
		return nil, fmt.Errorf("could not scan: %v", err)
	}
	return xys, nil
}

func plotData(path string, xys plotter.XYs) error {
	f, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("could not create %s: %v", path, err)
	}

	p, _ := plot.New()

	s, err := plotter.NewScatter(xys)
	if err != nil {
		return fmt.Errorf("could not create scatter: %v", err)
	}
	s.GlyphStyle.Shape = draw.CrossGlyph{}
	s.Color = color.RGBA{R: 255, A: 255}
	p.Add(s)

	var x, c float64
	x = 1.2
	c = -3

	l, points, err := plotter.NewLinePoints(plotter.XYs{
		{3, 3*x + c}, {20, 20*x + c},
	})
	if err != nil {
		return fmt.Errorf("could not create line: %v", err)
	}
	l.Color = color.RGBA{G: 255, A: 255}
	points.Shape = draw.CircleGlyph{}
	points.Color = color.RGBA{R: 255, A: 255}

	p.Add(l, points)

	err = p.Save(256, 256, "timeseries.png")
	if err != nil {
		log.Panic(err)
	}

	wt, err := p.WriterTo(256, 256, "png")
	if err != nil {
		return fmt.Errorf("could not create writer: %v", err)
	}
	_, err = wt.WriteTo(f)
	if err != nil {
		return fmt.Errorf("could not write to %s: %v", path, err)
	}

	if err := f.Close(); err != nil {
		return fmt.Errorf("could not close %s: %v", path, err)
	}
	return nil
}

What I'm doing wrong?

Thanks in advance!

Timeline Plot

Greetings!

I watched the episode about Gonum, but I don't understand how to create a time-based plot ..

I need to plot it:

2020/09/11,1336.44
2020/10/20,1936.44
2020/11/01,2005.11
2020/11/01,2005.24
2020/11/25,1994.25
2020/12/04,2594.25
2020/12/04,3194.25
2020/12/14,3185.49
2020/12/21,3172.35
2020/12/22,3342.35
2020/12/22,3172.35
2020/12/30,3161.34
2020/12/31,3011.34
2021/01/01,3078.34
2021/01/20,3038.34
2021/01/22,3028.34
2021/01/25,3328.34
2021/01/25,3628.34
2021/02/01,3758.34
2021/02/02,3733.26
2021/02/16,3709.38
2021/02/16,3859.38
2021/02/16,3709.38
2021/02/22,3673.38
2021/02/24,3619.38

I'm trying:

func readData(path string) (plotter.XYs, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var xys plotter.XYs
	s := bufio.NewScanner(f)
	for s.Scan() {
		var y float64
		var x float64

		_, err := fmt.Sscanf(s.Text(), "%f,%f", &x, &y)
		if err != nil {
			log.Printf("discarding bad data point %q: %v", s.Text(), err)
			continue
		}
		s := fmt.Sprintf("%f", x)
		date1, err := time.Parse("2006/02/01", s)
		date2, _ := strconv.Atoi(date1.String())
		x = float64(date2)
		xys = append(xys, struct{ X, Y float64 }{x, y})

		if err != nil {
			fmt.Println(err)
		}

	}
	if err := s.Err(); err != nil {
		return nil, fmt.Errorf("could not scan: %v", err)
	}
	return xys, nil
}

What I'm doing wrong?

Thanks in advance!

missing tool in go tool

in your post you have:

$ go tool seq.trace

but it should be

$ go tool trace seq.trace

you are missing there the trace. Not in the other code snippets though.

and I like the posts, much easier to follow than the videos 👍

episode idea: how about something that writes to db?

specially something that writes to google datastore or google database offerings. to be honest the documentation is not the best, there are two versions of everything for google app engine and not appengine, and they don't work ! specially if you wanted to try the db servers locally (using docker)

it would be a great thing if you make an episode of a full example of using google's database offerings in golang.

Episode 32 - Cobra - changes to cmd/root.go short and long descriptions don't update after a go install until I run go mod init

Thanks for the great videos. At ~7:50, you make a change to the Long description in the root command, run go install, and the code updates accordingly when you execute "todo". I did the same thing and found that my change to the short and long description would not update, even if I deleted my app binary from /bin and reran go install. It wasn't until I ran a go mod init in my app directory that things started to work as expected (i.e. code changes in the root command appeared after a go install...). Any idea why you were getting this to work without a go.mod file but I wasn't? Very perplexed.

Fanout channel to multiple channels

Would be great to see a video on a performant way of taking one channel of events and then fanning those events from that channel to n channels.

Obviously would be important to cover how to gracefully handle the shutdown of those channels without losing a event that is in flight.

Something like the following

40-csvql: applying projections results in 'does not have column' error

With the code in the video, if you try and apply a projection to a query, you get this error

mysql> select name from cities;
ERROR 1105 (HY000): unknown error: table "cities" does not have column "name"

I know this isn't demonstrated in the video

episode idea: handling multipart mails (html+text)

I can’t find a tutorial to create multipart mails with a text part and an utf-8 base64 encoded html part by using the standard library. The best I could find is this but it doesn’t seam to produce a valid mime encoding. An example using templates would be great.

My use case is the following. My Go program is doing a batch processing (e.g. backup, data integrity check, ...) and sends a report by mail. I have a python code that run every night and produce a text only report. When the report is long, it’s hard to locate the problems. I would now like to write the code in Go (because I can), and I’m stuck at generating a multipart mail with problems shown in red in the html part.

Another use case could be to send a multipart mail containing markdown text and its html encoding. The user would provide the markdown text.

Link to episode 40-csvql code is broken

Link to episode 40-csvql code is broken

32-cobra: removing dependency injection

I'm interested to know how you would now test the command handler functions given you have switched from dependency injection of the client to a package level variable. This appears to go against the principles you mentioned in an earlier episode.

Extensive use of "if err != nil" [Dude]

First of all thanks for your work, your talent and of course thanks for share your videos ( I'm new in Go and it's been quite helpful)

Watching them I saw you a lot of times using this expression:

if err != nil {log.Errorf(...)} }
or
if err != nil {return "", err}
or
if err != nil {return nil, fmt.Errorf(...)}

So I'm wondering if it will be a good solution create a function/s which gets the error and return it if it's needed, it's more about the reduction of lines and try to apply the DRY methodology.

It could be someting like this:

func myErr (err error) error{ if err != nil { return fmt.Error(...) } }

An then you can call it in just one line: myErr(err)

Thanks for your time!

the body of response for http.Get should close

The body of response for http.Get should close.

justforfunc/16-testing/webserver/main_test.go

Lines 85 to 89 in 90c277a

	res, err := http.Get(fmt.Sprintf("%s/double?v=2", srv.URL))
	if err != nil {
	t.Fatalf("could not send GET request: %v", err)
	}

episode idea: gomobile

• how is it similar/different with standard go
• project architecture: monorepo with go cli app + gomobile app + shared libs
• no more idea for now

episode idea: webasm

• how to do web as a gopher
• webasm best practices

suggest: simple mobile app to exchange public keys via qrcode

Hi,

I d like to suggest an app for future videos.

An app that runs on mobile, consume video feed to detect and read a qrcode, on the other end, the app can create/manage gpg identities in order to shows their public keys as a qrcode on the screen, so that another user can read it and decode the public key, you see ?

For the qrcode, i know there are several golang libs.
For the public keys, that be cool to introduce golang crypto https://godoc.org/golang.org/x/crypto/ and more specifically maybe https://godoc.org/golang.org/x/crypto/openpgp

For the mobile app, many things,

• is it cross compatible ios/android
• how to do/work in general
• how to interact with the video camera of the device

I have no idea if it is feasible, what do you think about it ?

Do i have to sign cla for suggestions too ? =)