Opentracing support

vendor/github.com/uber/jaeger-client-go/utils/rand.go

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+// Copyright (c) 2016 Uber Technologies, Inc.
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package utils
+
+import (
+	"math/rand"
+	"sync"
+)
+
+// lockedSource allows a random number generator to be used by multiple goroutines concurrently.
+// The code is very similar to math/rand.lockedSource, which is unfortunately not exposed.
+type lockedSource struct {
+	mut sync.Mutex
+	src rand.Source
+}
+
+// NewRand returns a rand.Rand that is threadsafe.
+func NewRand(seed int64) *rand.Rand {
+	return rand.New(&lockedSource{src: rand.NewSource(seed)})
+}
+
+func (r *lockedSource) Int63() (n int64) {
+	r.mut.Lock()
+	n = r.src.Int63()
+	r.mut.Unlock()
+	return
+}
+
+// Seed implements Seed() of Source
+func (r *lockedSource) Seed(seed int64) {
+	r.mut.Lock()
+	r.src.Seed(seed)
+	r.mut.Unlock()
+}