Exec invokes the specified Go toolchain or else prints an error and exits the process.

FilterEnv returns a copy of env with internal GOTOOLCHAIN environment variables filtered out.

HasAuto reports whether the GOTOOLCHAIN setting allows "auto" upgrades.

HasPath reports whether the GOTOOLCHAIN setting allows "path" upgrades.

NewerToolchain returns the name of the toolchain to use when we need to switch to a newer toolchain that must support at least the given Go version.

Select invokes a different Go toolchain if directed by the GOTOOLCHAIN environment variable or the user's configuration or go.mod file.

SwitchOrFatal attempts a toolchain switch based on the information in err and otherwise falls back to base.Fatal(err).

TestVersionSwitch is set in the test go binary to the value in $TESTGO_VERSION_SWITCH.

A Switcher collects errors to be reported and then decides between reporting the errors or switching to a new toolchain to resolve them.