gtr: Add Timestamp field to Package

When using the ReportBuilder, the Timestamp will by default be set to
the current local time.

pkg/gtr/builder.go

@@ -27,6 +27,7 @@ type ReportBuilder struct {
 
 	// default values
 	PackageName   string
+	TimestampFunc func() time.Time
 }
 
 // NewReportBuilder creates a new ReportBuilder.
@@ -37,6 +38,7 @@ func NewReportBuilder() *ReportBuilder {
 		buildErrors:   make(map[int]Error),
 		runErrors:     make(map[int]Error),
 		nextId:        1,
+		TimestampFunc: time.Now,
 	}
 }
 
@@ -136,6 +138,10 @@ func (b *ReportBuilder) CreatePackage(name, result string, duration time.Duratio
 		Duration: duration,
 	}
 
+	if b.TimestampFunc != nil {
+		pkg.Timestamp = b.TimestampFunc()
+	}
+
 	// Build errors are treated somewhat differently. Rather than having a
 	// single package with all build errors collected so far, we only care
 	// about the build errors for this particular package.

pkg/gtr/gtr.go

@@ -57,6 +57,7 @@ func (r *Report) IsSuccessful() bool {
 // Package contains build, test and/or benchmark results for a single package.
 type Package struct {
 	Name       string
+	Timestamp  time.Time
 	Duration   time.Duration
 	Coverage   float64
 	Output     []string