const text/template.mapError

4 uses

	text/template (current package)
		exec.go#L609: 		if s.tmpl.option.missingKey == mapError { // Treat invalid value as missing map key.
		exec.go#L665: 				case mapError:
		option.go#L17: 	mapError                             // Error out
		option.go#L66: 				t.option.missingKey = mapError