The package uses reflection to decode default types (int, string
etc.) from Redis map results (key-value pair sequences) into
struct fields where the fields are matched to Redis keys by tags.
Similar to how `encoding/json` allows custom decoders using
`UnmarshalJSON()`, the package supports decoding of arbitrary
types into struct fields by defining a `Decode(string) error`
function on types.
The field/type spec of every struct that's passed to Scan() is
cached in the package so that subsequent scans avoid iteration
and reflection of the struct's fields.
heyanfu