code health: unify messages format in datetime

After the patch all messages in datetime tests start with a capital
letter. All errors start with a lowecase letter [1].

1. https://github.com/golang/go/wiki/CodeReviewComments#error-strings

Author: oleg-jukovec

datetime/datetime.go

@@ -86,7 +86,7 @@ func NewDatetime(t time.Time) (*Datetime, error) {
 	seconds := t.Unix()
 
 	if seconds < minSeconds || seconds > maxSeconds {
-		return nil, fmt.Errorf("Time %s is out of supported range.", t)
+		return nil, fmt.Errorf("time %s is out of supported range", t)
 	}
 
 	dt := new(Datetime)

datetime/datetime_test.go

@@ -286,7 +286,7 @@ func (t *Tuple1) DecodeMsgpack(d *decoder) error {
 		return err
 	}
 	if l != 1 {
-		return fmt.Errorf("array len doesn't match: %d", l)
+		return fmt.Errorf("Array len doesn't match: %d", l)
 	}
 	err = d.Decode(&t.Datetime)
 	if err != nil {
@@ -315,7 +315,7 @@ func (ev *Event) DecodeMsgpack(d *decoder) error {
 		return err
 	}
 	if l != 2 {
-		return fmt.Errorf("array len doesn't match: %d", l)
+		return fmt.Errorf("Array len doesn't match: %d", l)
 	}
 	if ev.Location, err = d.DecodeString(); err != nil {
 		return err
@@ -326,7 +326,7 @@ func (ev *Event) DecodeMsgpack(d *decoder) error {
 	}
 	var ok bool
 	if ev.Datetime, ok = toDatetime(res); !ok {
-		return fmt.Errorf("datetime doesn't match")
+		return fmt.Errorf("Datetime doesn't match")
 	}
 	return nil
 }
@@ -352,7 +352,7 @@ func (c *Tuple2) DecodeMsgpack(d *decoder) error {
 		return err
 	}
 	if l != 3 {
-		return fmt.Errorf("array len doesn't match: %d", l)
+		return fmt.Errorf("Array len doesn't match: %d", l)
 	}
 	if c.Cid, err = d.DecodeUint(); err != nil {
 		return err

datetime/example_test.go

@@ -25,14 +25,14 @@ func Example() {
 	}
 	conn, err := tarantool.Connect("127.0.0.1:3013", opts)
 	if err != nil {
-		fmt.Printf("error in connect is %v", err)
+		fmt.Printf("Error in connect is %v", err)
 		return
 	}
 
 	var datetime = "2013-10-28T17:51:56.000000009Z"
 	tm, err := time.Parse(time.RFC3339, datetime)
 	if err != nil {
-		fmt.Printf("error in time.Parse() is %v", err)
+		fmt.Printf("Error in time.Parse() is %v", err)
 		return
 	}
 	dt, err := NewDatetime(tm)
@@ -47,7 +47,7 @@ func Example() {
 	// Replace a tuple with datetime.
 	resp, err := conn.Replace(space, []interface{}{dt})
 	if err != nil {
-		fmt.Printf("error in replace is %v", err)
+		fmt.Printf("Error in replace is %v", err)
 		return
 	}
 	respDt := resp.Data[0].([]interface{})[0].(Datetime)
@@ -60,7 +60,7 @@ func Example() {
 	var limit uint32 = 1
 	resp, err = conn.Select(space, index, offset, limit, tarantool.IterEq, []interface{}{dt})
 	if err != nil {
-		fmt.Printf("error in select is %v", err)
+		fmt.Printf("Error in select is %v", err)
 		return
 	}
 	respDt = resp.Data[0].([]interface{})[0].(Datetime)
@@ -71,7 +71,7 @@ func Example() {
 	// Delete a tuple with datetime.
 	resp, err = conn.Delete(space, index, []interface{}{dt})
 	if err != nil {
-		fmt.Printf("error in delete is %v", err)
+		fmt.Printf("Error in delete is %v", err)
 		return
 	}
 	respDt = resp.Data[0].([]interface{})[0].(Datetime)