tracer: add context to Options

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

tracer/context.go

@@ -46,3 +46,13 @@ func NewSpanContext(ctx context.Context, span Span) context.Context {
 	}
 	return context.WithValue(ctx, spanKey{}, span)
 }
+
+// SetOption returns a function to setup a context with given value
+func SetOption(k, v interface{}) Option {
+	return func(o *Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, k, v)
+	}
+}

tracer/options.go

@@ -1,6 +1,10 @@
 package tracer
 
-import "go.unistack.org/micro/v3/logger"
+import (
+	"context"
+
+	"go.unistack.org/micro/v3/logger"
+)
 
 // SpanOptions contains span option
 type SpanOptions struct {
@@ -28,6 +32,8 @@ type Options struct {
 	Logger logger.Logger
 	// Name of the tracer
 	Name string
+	// Context used to store custome tracer options
+	Context context.Context
 }
 
 // Option func signature