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

Go layer

• Description
  • Features:
• Install
  • Layer
  • Choosing a backend
    • LSP (gopls)
      • Debugger
    • go-mode (deprecated)
      • Documentation lookup binary
  • Binary dependencies
• Configuration
  • Execution
  • Indentation
  • Autoformat
  • Linting
  • Tests
  • Coverage
  • Guru
• Key bindings
  • Go commands (start with m):
  • Go Guru
  • Refactoring

Description

This layer adds extensive support for the Go programming language.

Features:

• Run gofmt / goimports on file save (see Autoformat)
• Auto-completion
• Source analysis using go-guru (see Guru)
• Refactoring with godoctor
• Edit struct field tags with gomodifytags
• Syntax checking with flycheck's built-in checkers or golangci-lint (see Linting)
• Test generation via go-gen-test (see Tests)
• Coverage profile visualization (see Coverage)
• List packages faster with gopkgs
• Fill a structure with default values using the fillstruct
• Gopls backend support (see LSP backend)
• Interactive debugger with LSP using dap-mode

Install

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.

Choosing a backend

Basically you have to choose between multiple language backends. This choice defines mainly which kind of IDE features spacemacs can deliver.

Alternatively if non is set the lsp backend will be automatically chosen if the layer lsp is used otherwise go-mode will be used.

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

LSP (gopls)

This is the official IDE configuration for the current go versions. It includes auto-completion and syntax checking support.

It is based on an external development server written in go itself, which must be installed separately before this layer can be used.

Starting and stopping the server is done by emacs so you normally won't notice it happen.

Detailed bindings and configuration can be found in lsp layer description.

To choose this backend set the layer variable go-backend:

  (go :variables go-backend 'lsp)

You also need to install gopls as the language server implementation and add it to your PATH. If your go environment is properly prepared you can simply run below command to install:

  GO111MODULE=on go get -v golang.org/x/tools/gopls@latest

Debugger

Using the dap layer you'll get access to a graphical debugger integration. To do so add the layer dap to your dotfile. For a complete list of key bindings see the dap layer description.

go-mode (deprecated)

This was the old elisp based go backend. Since the introduction of go-modules this has stopped working and will not be patched.

To choose it nevertheless set the layer variable go-backend:

  (go :variables go-backend 'go-mode)

You will also need the following dependencies for auto-completion:

  go get -u -v github.com/mdempsky/gocode
  go get -u -v github.com/zmb3/gogetdoc

Documentation lookup binary

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 built-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 independently from where they have been added. This is also the recommended choice from go-mode.el.

To choose gocode nothing more needs to be done. To use gogetdoc you need to set the layer variable:

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

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 the go install ./... command on every file change.

Binary dependencies

This section lists dependencies which are independent of the language backend, most are installed directly via go get:

  GO111MODULE=on CGO_ENABLED=0 go get -v -trimpath -ldflags '-s -w' github.com/golangci/golangci-lint/cmd/golangci-lint
  go get -u -v golang.org/x/tools/cmd/godoc
  go get -u -v golang.org/x/tools/cmd/goimports
  go get -u -v golang.org/x/tools/cmd/gorename
  go get -u -v golang.org/x/tools/cmd/guru
  go get -u -v github.com/cweill/gotests/...
  go get -u -v github.com/davidrjenni/reftools/cmd/fillstruct
  go get -u -v github.com/fatih/gomodifytags
  go get -u -v github.com/godoctor/godoctor
  go get -u -v github.com/haya14busa/gopkgs/cmd/gopkgs
  go get -u -v github.com/josharian/impl
  go get -u -v github.com/rogpeppe/godef

Configuration

Execution

By default, the go run command is go run. If you want to use a different command or run with environment variables, set the layer variable go-run-command.

  (go :variables go-run-command "ENV_VAR=foo go run")

To run the current main package with command line arguments, set the value of go-run-args as a 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 conflicts, i.e.

  (go :variables go-tab-width nil)

Autoformat

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

  (go :variables go-format-before-save t)

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

  (go :variables gofmt-command "goimports")

Linting

If you wish to use golangci-lint, set the following layer variable to non-nil:

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

Check golangci-lint and flycheck-golangci-lint for more details.

Please remember that without properly configured flycheck-golangci-lint variables golangci-lint may not run as expected. The recommended way is to use a .golangi.yml in your project. But if this is not possible you can also set global command line flags for golangci-lint. Especially important is the selection of which linters to run and whether to lint test files too.

It may happen from time to time that golangci-lint is not able to parse a buffers content properly. This normally happens when there are basic errors in the file which prevent more complex analytics to run. In this case a set of errors will be shown at the top of the current buffer which are not properly parsed by flycheck. Spacemacs still shows basic errors in your buffer. When these have been fixed golangci-lint will regenerate and further diagnostic data will be made available.

When this happens please report a bug to `golangci-lint` they are working hard to fix these.

Tests

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

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.

By default, the go test command is go test. If you want to use a different command or test with environment variables, set the layer variable go-test-command.

  (go :variables go-test-command "ENV_VAR=foo go test")

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

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

Coverage

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

Guru

If you would like to use the Go Guru bindings in your work, 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 it with - to exclude a package from searching.

Key bindings

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 (with gomodifytags)
SPC m r F	Remove field tags (with gomodifytags)
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 (with go-fillstruct)
SPC m r t	Toggle declaration and assignment