by BeMasher:

I find that often when I'm writing types I need to apply special fmt formatting to
specific fields in structs while leaving the rest as the default "v" fmt verb.
Implementing Stringer on the type becomes cumbersome when I only need to modify the
formatting for one or two fields in a struct.

For example the following type requires a tedious String function where adding or
removing fields requires modification in the type and the String function:

type Foo {
    Bar  []byte
    Baz1 uint32
    Baz2 uint32
    Baz3 uint32
    Baz4 uint32
    Baz5 uint32
}

func (f Foo) String() string {
    return fmt.Sprintf("{Bar:%s Baz1:%d Baz2:%d Baz3:%d Baz4:%d Baz5:%d}", f.Bar, f.Baz1, f.Baz2, f.Baz3, f.Baz4, f.Baz5)
}

One solution is to add a tag to the Bar field specifying the verb to use since it is the
only field that needs to be formatted differently from the standard "v" verb.
This allows me to use fmt functions that don't require a format string without
constantly having to update the String method.

type Foo {
    Bar  []byte `fmt:"s"`
    Baz1 uint32
    Baz2 uint32
    Baz3 uint32
    Baz4 uint32
    Baz5 uint32
}

Printing using fmt.Println (or other non-formatting) then produces the desired result
without needing to implement Stringer for the type.

Need to determine when tags will be used or ignored, particularly when a format string
is supplied.