manucorporat / asset

Reference asset files easier

#asset-go

asset helps golang developers to reference external assets inside binaries.

##The goal

• Configurable base path for assets
• Relative paths done right

###What wait! where is the trouble? Golang does not have a built-in bundle manager like many popular languages do. ie. It does not generate a portable .app .jar container that includes everything the app needs (binaries and assets).

###Possible solution: Absolute paths

file, err := os.Open("/var/www/image.png")

Disadvanges:

• Your assets and binaries are spread around the system.
• Tricky for version control
• No cross platform

###Possible solution: Relative paths

file, err := os.Open("image.png")

Disadvanages:

• The binary MUST by executed in the same working path.

$ /var/bin/myserver

does not work. You have to change the working path in order to get it run properly:

$ cd /var/bin/
$ ./myserver

##asset.go solution

file, err := os.Open(asset.Path("image.png"))

asset knows where the executable is located, so there is not need to change the working path.

##Understanding asset

If the binary is located at /go/bin/myserver .

func main() {
   fmt.Println(asset.Path("image.png"))
}

$ cd /root
$ /go/bin/myserver
/go/bin/myserver/image.png

$ myserver
/go/bin/myserver/image.png

$ cd test
$ ./symlink_myserver
/go/bin/myserver/image.png

`asset.Path() returns the same path, no matter how the binary is executed.

###Configuring asset asset.Configure(DEFAULT_VALUE, INPUT_FLAGS)

Let's focus in DEFAULT_VALUE by the moment.

func init() {
   asset.Configure("resources", asset.NoInput)
   fmt.Println(asset.Path("image.png"))
}

/go/bin/server/resources/image.png

How about an absolute path?

asset.Configure("/var/www/resources", asset.NoInput)
fmt.Println(asset.Path("image.png"))

/var/www/resources/image.png

####INPUT_FLAGS

func init() {
   asset.EnvVariableName = "SERVER_ASSETS"
   asset.Configure("", asset.Environment)
   fmt.Println(asset.Path("image.png"))
}

Now you can change the base path with an environment variables:

$ export SERVER_ASSETS="/var/myserver/resources"
$ myserver

/var/myserver/resources/image.png

A flag can be also used:

asset.Configure("", asset.Environment | asset.Flag)

myserver -apath="/myassets"