type missingKeyAction … const mapInvalid … const mapZeroValue … const mapError … type option … // Option sets options for the template. Options are described by // strings, either a simple string or "key=value". There can be at // most one equals sign in an option string. If the option string // is unrecognized or otherwise invalid, Option panics. // // Known options: // // missingkey: Control the behavior during execution if a map is // indexed with a key that is not present in the map. // // "missingkey=default" or "missingkey=invalid" // The default behavior: Do nothing and continue execution. // If printed, the result of the index operation is the string // "<no value>". // "missingkey=zero" // The operation returns the zero value for the map type's element. // "missingkey=error" // Execution stops immediately with an error. func (t *Template) Option(opt ...string) *Template { … } func (t *Template) setOption(opt string) { … }