Build constraints and vendoring

A build constraint, also known as a build tag, is a line comment that outlines the conditions under which a file is included in the package. These tags can specify requirements such as the operating system, architecture, Go version, compiler, cgo support, or other target system needs. In the example below, we declare that this file is for the target system meeting the following criteria:

• //+build darwin,cgo linux is the older syntax for build tags, still recognized in Go. It specifies two sets of conditions:

  • darwin,cgo: Include in the build when compiling for the darwin platform (macOS) and when cgo is enabled. cgo enables the inclusion of C code in Go programs.

  • linux: Include when compiling for the Linux platform.

  The space acts as an OR operator, meaning the file should be included for macOS with cgo enabled or for Linux.

• //go:build (darwin && cgo) || linux is the newer syntax for build tags, introduced in Go 1.17, using a more explicit boolean expression format:

  • (darwin && cgo) || linux: The file should be included in the build for macOS with cgo enabled or for Linux, identical to the above condition.

GoLand can use these constraints to decide what files must be ignored during validation, resolving, and symbol suggestions. If the file does not satisfy the requirements of the target system, GoLand displays a notification. For example, the following conditions on the screenshot will conflict with settings from the Configure build constraints for your project procedure.

Description of Build Tags fields

For more information about build tags or constraints, see Build constraints at pkg.go.dev.

Field	Build Tags	Description
Operating System	GOOS	Specifies the operating system you're compiling your code for, such as linux or windows.
Architecture	GOARCH	Defines the CPU architecture for your code, like amd64 or arm.
Go Version	GOVERSION	Tells you the Go version installed. It is the same version you see when you run go version.
Compiler		Chooses the compiler, like gccgo or gc, based on what is available in your runtime.
CGO Support	CGO_ENABLED	Shows if cgo is enabled (1) or disabled (0), affecting whether you can include C code.
Custom Tags		Any build tags introduced by the //go:build comment line. For example, in the following screenshot, the goexperiment.rangefunc build tag enables iteration over a function from Go Experiments.
Experiments	GOEXPERIMENT	A list of Go toolchain experiments you can turn on or off. Mainly for developers working on Go itself.

//+build darwin,cgo linux

//go:build (darwin && cgo) || linux

With the vendoring mode enabled, you build your application only with dependency packages that are stored inside your project under the vendor directory. In this mode, Go commands ignore dependency descriptions in go.mod and assume that the vendor directory holds the correct copies of dependencies. By default, when you use Go modules, the vendor directory is ignored during the build.

In Go 1.14 RC, automatic vendoring mode became a built-in Go feature. Starting from Go 1.14 RC, GoLand also enables automatic vendoring mode by default. You can disable vendoring per project, for example, when you have a monorepo containing the vendor folder used by another language.

You can control automatic vendoring by using the Enable vendoring support automatically checkbox. When the checkbox is selected, automatic vendoring is enabled. So, if you add the vendor directory to the module, the IDE uses it. If you remove the directory, GoLand uses the global Go Modules cache.