I am currently developing an application using Flask, WTForms, SQLAlchemy and the corresponding Flask extensions to glue them all together. I am considering moving to Go in the future because reasons. Are there any libraries in Go that allow me to map web forms to models and parameterise validation the same way WTForms does?
There is not something as "complete" as WTForms for Go (yet): you will find that Go packages are a little more modular than even Flask's.
You can cover the POST form to Go struct with either goforms or gorilla/schema.
I'd also recommend sqlx as a nice shim on top of database/sql.