null 
import "gopkg.in/guregu/null.v3"
null is a library with reasonable options for dealing with nullable SQL and JSON values
There are two packages: null and its subpackage zero.
Types in null will only be considered null on null input, and will JSON encode to null. If you need zero and null be considered separate values, use these.
Types in zero are treated like zero values in Go: blank string input will produce a null zero.String, and null Strings will JSON encode to "". Zero values of these types will be considered null to SQL. If you need zero and null treated the same, use these.
All types implement sql.Scanner and driver.Valuer, so you can use this library in place of sql.NullXXX. All types also implement: encoding.TextMarshaler, encoding.TextUnmarshaler, json.Marshaler, and json.Unmarshaler.
null package
import "gopkg.in/guregu/null.v3"
null.String
Nullable string.
Marshals to JSON null if SQL source data is null. Zero (blank) input will not produce a null String. Can unmarshal from sql.NullString JSON input or string input.
null.Int
Nullable int64.
Marshals to JSON null if SQL source data is null. Zero input will not produce a null Int. Can unmarshal from sql.NullInt64 JSON input.
null.Float
Nullable float64.
Marshals to JSON null if SQL source data is null. Zero input will not produce a null Float. Can unmarshal from sql.NullFloat64 JSON input.
null.Bool
Nullable bool.
Marshals to JSON null if SQL source data is null. False input will not produce a null Bool. Can unmarshal from sql.NullBool JSON input.
null.Time
Marshals to JSON null if SQL source data is null. Uses time.Time's marshaler. Can unmarshal from pq.NullTime and similar JSON input.
zero package
import "gopkg.in/guregu/null.v3/zero"
zero.String
Nullable string.
Will marshal to a blank string if null. Blank string input produces a null String. Null values and zero values are considered equivalent. Can unmarshal from sql.NullString JSON input.
zero.Int
Nullable int64.
Will marshal to 0 if null. 0 produces a null Int. Null values and zero values are considered equivalent. Can unmarshal from sql.NullInt64 JSON input.
zero.Float
Nullable float64.
Will marshal to 0 if null. 0.0 produces a null Float. Null values and zero values are considered equivalent. Can unmarshal from sql.NullFloat64 JSON input.
zero.Bool
Nullable bool.
Will marshal to false if null. false produces a null Float. Null values and zero values are considered equivalent. Can unmarshal from sql.NullBool JSON input.
zero.Time
Will marshal to the zero time if null. Uses time.Time's marshaler. Can unmarshal from pq.NullTime and similar JSON input.
Bugs
json's ",omitempty" struct tag does not work correctly right now. It will never omit a null or empty String. This might be fixed eventually.
License
BSD