spacemacs/layers/+lang/go/README.org

GO layer

• Description
  • Features:
• Install
  • Pre-requisites
  • LSP backend
  • Layer
• Configuration
  • Indentation
  • Tests
  • Guru
  • Autocomplete
• Working with Go
  • Go commands (start with m):
  • Go Guru
  • Refactoring

Description

This layer adds extensive support for go to Spacemacs.

Features:

• gofmt/goimports on file save (to enable, see Configuration)
• Auto-completion using go-autocomplete (with the auto-completion layer)
• Source analysis using go-guru
• Refactoring with godoctor
• Edit struct field tag with gomodifytags
• Linting with flycheck's built-in checkers or flycheck-gometalinter
• Coverage profile visualization
• Test generation with go-gen-test
• Get packages faster with gopkgs
• Fill a structure with default values using the fillstruct
• LSP backend

Install

Pre-requisites

You will need gocode, gogetdoc, godef, godoctor and many others to get all the goodies of this layer:

  go get -u -v github.com/mdempsky/gocode
  go get -u -v github.com/rogpeppe/godef
  go get -u -v golang.org/x/tools/cmd/guru
  go get -u -v golang.org/x/tools/cmd/gorename
  go get -u -v golang.org/x/tools/cmd/goimports
  go get -u -v golang.org/x/tools/cmd/godoc
  go get -u -v github.com/zmb3/gogetdoc
  go get -u -v github.com/cweill/gotests/...
  go get -u github.com/haya14busa/gopkgs/cmd/gopkgs
  go get -u -v github.com/davidrjenni/reftools/cmd/fillstruct
  go get -u github.com/josharian/impl

If you wish to use a linters aggregator tool, you can enable gometalinter or golangci-lint.

If you wish to use gometalinter set the value of go-use-gometalinter to t:

  (go :variables go-use-gometalinter t)

and install the tool:

  go get -u -v github.com/alecthomas/gometalinter
  gometalinter --install --update

For more information read gometalinter README.md and flycheck-gometalinter README.md

If you wish to use golangci-lint set the value of go-use-golangci-lint to t:

  (go :variables go-use-golangci-lint t)

and install the tool:

  go get -u github.com/golangci/golangci-lint/cmd/golangci-lint

For more information read golangci-lint README.md and flycheck-golangci-lint README.md

If you wish to use godoctor for refactoring, install it too:

  go get -u -v github.com/godoctor/godoctor
  go install github.com/godoctor/godoctor

If you want to use gomodifytags to edit field tags, install it too:

  go get -u -v github.com/fatih/gomodifytags

Make sure that the gocode executable is in your PATH. For information about setting up $PATH, check out the corresponding section in the FAQ (SPC h f $PATH RET).

For best results, make sure that the auto-completion and syntax-checking layers are enabled as well.

LSP backend

To enable the LSP backend set the layer variable go-backend:

  (go :variables go-backend 'lsp)

You also need to install the Go Language Server. Consult the installation command for the desired language server found at lsp-mode for instructions.

Backend can be chosen on a per project basis using directory local variables (files named .dir-locals.el at the root of a project), an example to use the go-mode backend:

  ;;; Directory Local Variables
  ;;; For more information see (info "(emacs) Directory Variables")

  ((go-mode (go-backend . go-mode)))

Note: you can easily add a directory local variable with SPC f v d.

Layer

To use this configuration layer, add it to your ~/.spacemacs. You will need to add go to the existing dotspacemacs-configuration-layers list in this file.

Configuration

To run gofmt before save, set the value to a non-nil, e.g.

  (setq go-format-before-save t)

To use a different formatter, set the value of gofmt-command, e.g.

  (setq gofmt-command "goimports")

or

  (go :variables gofmt-command "goimports")

To run current main package with command line arguments, set the value of go-run-args as file local variable, e.g.

  // Local Variables:
  // go-run-args: "--output run.log"
  // End:

Indentation

By default, the tab width in Go mode is 8 spaces. To use a different value set the layer variable go-tab-width, e.g.

  (go :variables go-tab-width 4)

If you're using .editorconfig in your project, set the value to nil to avoid confliction, e.g.

  (go :variables go-tab-width nil)

Tests

If you're using gocheck in your project you can use the go-use-gocheck-for-testing variable to enable suite testing and to get single function testing to work.

go-coverage-display-buffer-func controls how go-coverage should display the coverage buffer. See display-buffer">display-buffer for a list of possible functions. The default value is display-buffer-reuse-window.

Tests are run in a compilation buffer displayed in a popup window that can be closed by pressing C-g from any other window. The variable go-test-buffer-name can be customized to set the output buffer name.

To provide additional arguments to go test, specify go-use-test-args.

  (go :variables go-use-test-args "-race -timeout 10s"

Guru

Go Oracle has been deprecated as of October 1, 2016, it's replacement is go-guru.

If you would like to use the goguru bindings in your work, you will need to install it, and in your project you will need to set the scope with SPC m f o. The scope is a comma separated set of packages, and go=’s recursive operator is supported. In addition, you can prefix with =- to exclude a package from searching.

In addition, GOPATH must be set prior to go-guru initialization.

Autocomplete

For auto-completion there are actually two choices. First there is the classic gocode. This has been around for quite a long time now, however gocode has many shortcomings like not being able to show documentation for build-in objects or being fully dependent on installed binary files to provide its suggestions.

A more modern and complete solution is provided by gogetdoc which is able to precisely detect all documentations in your go projects independent on where they have been added. This is also the choice recommended from go-mode.el.

To choose gocode nothing more needs to be done. To use gogetdoc you need to set

  (go :variables godoc-at-point-function 'godoc-gogetdoc)

in your dotfile.

If you choose to use gocode there are some suggestions to improve its results. As gocode uses the output from installed binary files to provide its suggestions. You have a few options to ensure you always get up to date suggestions:

• Run go install ./... in your package directory when you make a file change.
• Run gocode set autobuild true to have gocode attempt to run go install ./... for you.
• You can configure your task runner to run go install ./... command on every file change.

Working with Go

Go commands (start with m):

Key binding	Description
SPC m =	run "go fmt"
SPC m e b	go-play buffer
SPC m e d	download go-play snippet
SPC m e r	go-play region
SPC m g a	jump to matching test file or back from test to code file
SPC m g c	open a clone of the current buffer with a coverage info (go tool cover -h for help)
SPC m g g	go jump to definition
SPC m h h	godoc at point
SPC m i a	add import
SPC m i g	goto imports
SPC m i r	remove unused import
SPC m r n	go rename
SPC m t P	run "go test" for the current package and all packages under it
SPC m t g f	generate tests for all exported functions
SPC m t g F	generate tests for all functions
SPC m t g g	DWIM generate test for the function in the active region
SPC m t p	run "go test" for the current package
SPC m t s	run "go test" for the suite you're currently in (requires gocheck)
SPC m t t	run "go test" for the function you're currently in (while you're in a _.test.go file)
SPC m x x	run "go run" for the current 'main' package

Go Guru

Key binding	Description
SPC m f <	go-guru show possible callers
SPC m f >	go-guru show call targets
SPC m f c	go-guru show channel sends/receives
SPC m f d	go-guru describe symbol at point
SPC m f e	go-guru show possible contants/types for error value
SPC m f f	go-guru show free variables
SPC m f i	go-guru show implements relation
SPC m f j	go-guru jump to symbol definition
SPC m f o	go-guru set analysis scope
SPC m f p	go-guru show what the select expression points to
SPC m f r	go-guru show referrers
SPC m f s	go-guru show callstack

Refactoring

Key binding	Description
SPC m r d	Add comment stubs
SPC m r e	Extract code as new function
SPC m r f	Add field tags
SPC m r F	Remove field tags
SPC m r i	Generate method stubs for implementing an interface (go-impl)
SPC m r n	Rename (with godoctor)
SPC m r N	Rename (with go-rename)
SPC m r s	Fill structure with default values
SPC m r t	Toggle declaration and assignment