Go template options
https://pkg.go.dev/text/template#Template.Option
"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.