[#12] Fix int-like fields encoding

Do it in journal similar to how we do it in zap.
1. Duration should take the form of "12s".
2. Uint64 should be encoded without sign.
3. Bool is better be true/false instead of 0/1.
4. Float64 should be float, not IEEE 754 bits cast to int64.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

zapjournald.go

@@ -2,7 +2,9 @@ package zapjournald
 
 import (
 	"fmt"
+	"math"
 	"strconv"
+	"time"
 
 	"github.com/ssgreg/journald"
 	"go.uber.org/zap/zapcore"
@@ -139,20 +141,29 @@ func getFieldValue(f zapcore.Field) interface{} {
 		zapcore.ErrorType,
 		zapcore.SkipType:
 		return f.Interface
-	case zapcore.DurationType,
+	case zapcore.DurationType:
-		zapcore.Float64Type,
+		return time.Duration(f.Integer).String()
-		zapcore.Float32Type,
+	case zapcore.Float64Type:
-		zapcore.Int64Type,
+		// See https://github.com/uber-go/zap/blob/v1.26.0/buffer/buffer.go#L79
+		f := math.Float64frombits(uint64(f.Integer))
+		return strconv.FormatFloat(f, 'f', -1, 64)
+	case zapcore.Float32Type:
+		f := math.Float32frombits(uint32(f.Integer))
+		return strconv.FormatFloat(float64(f), 'f', -1, 32)
+	case zapcore.Int64Type,
 		zapcore.Int32Type,
 		zapcore.Int16Type,
-		zapcore.Int8Type,
+		zapcore.Int8Type:
+		return strconv.FormatInt(f.Integer, 10)
+	case
 		zapcore.Uint64Type,
 		zapcore.Uint32Type,
 		zapcore.Uint16Type,
 		zapcore.Uint8Type,
-		zapcore.UintptrType,
+		zapcore.UintptrType:
-		zapcore.BoolType:
+		return strconv.FormatUint(uint64(f.Integer), 10)
-		return f.Integer
+	case zapcore.BoolType:
+		return strconv.FormatBool(f.Integer == 1)
 	case zapcore.StringType:
 		return f.String
 	case zapcore.TimeType:
@@ -160,7 +171,7 @@ func getFieldValue(f zapcore.Field) interface{} {
 			// for example: zap.Time("k", time.Unix(100900, 0).In(time.UTC)) - will produce: "100900000000000 UTC" (result in nanoseconds)
 			return fmt.Sprintf("%d %v", f.Integer, f.Interface)
 		}
-		return f.Integer
+		return strconv.FormatUint(uint64(f.Integer), 10)
 	default:
 		panic(fmt.Sprintf("unknown field type: %v", f))
 	}