undefined: jsonpath.PlaceholderExtension, how to fix it?

[fengnex]

One official example of jsonpath uses jsonpath.PlaceholderExtension, but when we ran it and got an error "undefined: jsonpath.PlaceholderExtension", how to fix it?

[zeisss]

Not part of the project and probably a year too late, but anyway: Did you import the module correctly? What example did you use?

PlaceholderExtension() seems to be defined here: https://github.com/PaesslerAG/jsonpath/blob/master/jsonpath.go#L65-L67 so generally it should work.
The tests in https://github.com/PaesslerAG/jsonpath/blob/master/placeholder_test.go show an example usage.