Get returns a value for a given key.

GetAll returns all keys/values in the current child process environment.

GetGOBIN returns GOBIN environment variable as a string.

GetGOPATH returns GOPATH environment variable as a string.

GetRuntimeEnv returns the value of runtime environment variable, that is set by running following command: `go env -w key=value`.

MustGet returns a value by key.

MustSet sets a value in the ENV copy and the child process environment.

Set sets a value in the ENV copy.