Added code to scan null values from the database

decimal.go

@@ -579,7 +579,14 @@ func (d Decimal) MarshalJSON() ([]byte, error) {
 
 // Scan implements the sql.Scanner interface for database deserialization.
 func (d *Decimal) Scan(value interface{}) error {
-	// first try to see if the data is stored in database as a Numeric datatype
+	// check to see if we have a nil value, return a zero value and exp
+	if value == nil {
+		d.value = zeroInt
+		d.exp = 0
+		return nil
+	}
+
+	// try to see if the data is stored in database as a Numeric datatype
 	switch v := value.(type) {
 
 	case float64:

decimal_test.go

@@ -1117,6 +1117,21 @@ func TestDecimal_Max(t *testing.T) {
 	}
 }
 
+func TestDecimal_ScanNil(t *testing.T) {
+	a := Decimal{}
+	expected := Decimal{
+		value: zeroInt,
+		exp:   0,
+	}
+	err := a.Scan(nil)
+	if err != nil {
+		t.Error(err)
+	}
+	if !a.Equal(expected) {
+		t.Errorf("%s does not equal to %s", a, expected)
+	}
+}
+
 func TestDecimal_Scan(t *testing.T) {
 	// test the Scan method that implements the
 	// sql.Scanner interface