Assuming this struct:

type S struct {
  Name string
  Number int
}

The way to use an instance of the structure is to add it to a Context:

ctx := Context{
  "mystruct": S
}

And the way to use it in a template is to access the struct members using the Go convention: variables starting with an uppercase letter are exported:

Hello {{ mystruct.Name }}. This is number {{ mystruct.Number }}.

Which works ok, but can be a bit ugly when switching from lowercase names to uppercase. Why not introduce a Go struct tag which renames fields for use in Pongo2? Something like this:

type S struct {
  Name string `pongo2:"name"`
  Number int  `pongo2:"a_number"`
}

This would allow more flexibility and consistency in templates by writing:

Hello {{ mystruct.name }}. This is number {{ mystruct.a_number }}.