A tool to be used with ‘go generate’ to embed external resources into Go code to create single file executables without any dependencies.

Scenario

An often used scenario in developing go applications is to embed external resources to be able to create only one binary without any dependencies. There are a number of existing packages solving this problem, like bindata, packr or packger and if you are looking for fancy features and unicorns you should probably better go there. Usually they are creating a kind of virtual file system. Usually this really a lot more than I need for my simple use case on including one or two files into a small CLI program.

This package ‘mule’ (the kinda donkey carrying huge loads) takes a much simpler approach. It just generates a single .go file for each resource you want to embed, including the encoded resource wrapped in a function to access it.

It is intended to be run by go generate, though that is not required.

Installation

go get github.com/wlbr/mule

Usage

Simply add a line

//go:generate mule mybinary.file

to one of your source files for each resource you want to embed. Every time you run a ‘go generate’ in the corresponding folder, the file ‘mybinary.go’ will be created. It contains a function ‘mybinaryResource’ returning the resource as a []byte.

See mulex.go for a very, very simple example.

You may use ‘mule mybinary.file’ directly on the command line.

Switches

Usage of mule: mule [switches] resourcefilename
-e
export the generated, the resource returning function. Default (false) means the function will not be exported.

-f
no formatting of the generated source. Default false means source will be formatted with gofmt.

-n string
name of generated, the resource returning function. Its name will have ‘Resource’ attached. Will be set to $(basename -s .ext outputfile) if empty (default). Take care of “-“ within the name, especially when the name is calculated from the resources file name. A ‘-‘ would create an invalid go function name

-o string

name of output file. Defaults to name of resource file excluding extension + ‘.go’.

-p string
name of package to be used in generated code (default “main”).

-t string
name of alternate code generation template file. If empty (default), then the embedded template will be used. Template variables supplied are: .Name, .Package, .Content

See https://github.com/wlbr/mule for details.