go/src/cmd/go/internal/base/goflags.go

var goflags …

// GOFLAGS returns the flags from $GOFLAGS.
// The list can be assumed to contain one string per flag,
// with each string either beginning with -name or --name.
func GOFLAGS() []string { … }

// InitGOFLAGS initializes the goflags list from $GOFLAGS.
// If goflags is already initialized, it does nothing.
func InitGOFLAGS() { … }

type boolFlag …

// SetFromGOFLAGS sets the flags in the given flag set using settings in $GOFLAGS.
func SetFromGOFLAGS(flags *flag.FlagSet) { … }

// InGOFLAGS returns whether GOFLAGS contains the given flag, such as "-mod".
func InGOFLAGS(flag string) bool { … }