code: func lookupVar(v string) (string, bool) {
  	// TODO: optimize if the number of variable names grows
  	switch v {
  	case "FABRIC_SDK_GO_PROJECT_PATH":
  		return metadata.GetProjectPath(), true
  	case "GOPATH":
  		return goPath(), true
  	case "CRYPTOCONFIG_FIXTURES_PATH":
  		return metadata.CryptoConfigPath, true
  	}
  	return os.LookupEnv(v)
  }
docs: // lookupVar returns the value of the variable.
  // The local variable table is consulted first, followed by environment variables.
  // Returns false if the variable doesn't exist.