many fixes for lint and context.Context usage (#5)

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

tracer/noop.go

@@ -2,24 +2,34 @@ package tracer
 
 import "context"
 
-type NoopTracer struct{}
+type noopTracer struct {
+	opts Options
+}
 
-func (n *NoopTracer) Init(...Option) error {
+// Init initilize tracer
+func (n *noopTracer) Init(opts ...Option) error {
+	for _, o := range opts {
+		o(&n.opts)
+	}
 	return nil
 }
 
-func (n *NoopTracer) Start(ctx context.Context, name string) (context.Context, *Span) {
+// Start starts new span
+func (n *noopTracer) Start(ctx context.Context, name string) (context.Context, *Span) {
 	return nil, nil
 }
 
-func (n *NoopTracer) Finish(*Span) error {
+// Finish finishes span
+func (n *noopTracer) Finish(*Span) error {
 	return nil
 }
 
-func (n *NoopTracer) Read(...ReadOption) ([]*Span, error) {
+// Read reads span
+func (n *noopTracer) Read(...ReadOption) ([]*Span, error) {
 	return nil, nil
 }
 
+// NewTracer returns new noop tracer
 func NewTracer(opts ...Option) Tracer {
-	return &NoopTracer{}
+	return &noopTracer{opts: NewOptions(opts...)}
 }