map.go
func Map(dst, src interface{}, opts ...func(*Config)) error {
	return _map(dst, src, opts...)
}
func Map(dst, src interface{}, opts ...func(*Config)) error {
	return _map(dst, src, opts...)
}
// Map sets fields' values in dst from src.
// src can be a map with string keys or a struct. dst must be the opposite:
// if src is a map, dst must be a valid pointer to struct. If src is a struct,
// dst must be map[string]interface{}.
// It won't merge unexported (private) fields and will do recursively
// any exported field.
// If dst is a map, keys will be src fields' names in lower camel case.
// Missing key in src that doesn't match a field in dst will be skipped. This
// doesn't apply if dst is a map.
// This is separated method from Merge because it is cleaner and it keeps sane
// semantics: merging equal types, mapping different (restricted) types.