
In replace directives, the IDE would not download or delete missed dependencies, and the lines with these unused dependencies would be marked red.
#Goland blog mod
Sync dependencies: fetches and downloads missed dependencies and removes unused ones by calling go mod tidy/vendor. To work with dependencies, you can select between the following options: Select the Enable Go modules integration checkbox. Open settings by pressing Ctrl+Alt+S and navigate to Go | Go.

If you pulled your Go modules project from Github, you need to enable Go modules manually. If you create a new Go modules project in the IDE, Go modules are already enabled. The version of each Go Module is shown in a dimmed font color to help you distinguish between them. In the Project tool window ( View | Tool Windows | Project), Go modules are displayed with their full import path. For more information about vendoring, see Vendoring. But you can configure this setting for earlier Go versions. Note that automatic vendoring mode became a built-in Go feature in Go 1.14 RC. (Optional) To use vendoring mode, select the Enable vendoring support automatically checkbox. Read more about environment variables in the Environment variables section. For example, the GOPROXY environment variable. In the Environment field, specify environment variables that you need for your project. For more information about installing Go SDK, see Installing Go SDK.

#Goland blog install
To change or install a new version of Go SDK, click the Add SDK… button and select Local… to choose the Go SDK version on your hard drive, or select Download… to download Go SDK from the official repository. Usually, the location is defined automatically. In the GOROOT field, specify the location of your Go installation. In the Location field, specify the path where you want to store your project. Create a project with Go modules integration

With Go modules, you do not need to keep your project files under GOPATH and can easily manage dependencies in your project. By default, GoLand suggests creating a Go modules project.
