Localize the scope of context.WithCancel for every DAG.Get

Instead put it inside of DAG.Get.
The fix is applied only in the case when the context.WithCancel
before a DAG.Get is also used later on in the scope.

License: MIT
Signed-off-by: rht <rhtbot@gmail.com>

merkledag.go

@@ -93,6 +93,8 @@ func (n *dagService) Get(ctx context.Context, k key.Key) (*Node, error) {
 	if n == nil {
 		return nil, fmt.Errorf("dagService is nil")
 	}
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
 
 	b, err := n.Blocks.GetBlock(ctx, k)
 	if err != nil {

traverse/traverse.go

@@ -3,7 +3,6 @@ package traverse
 
 import (
 	"errors"
-	"time"
 
 	"github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
 
@@ -67,10 +66,7 @@ func (t *traversal) callFunc(next State) error {
 func (t *traversal) getNode(link *mdag.Link) (*mdag.Node, error) {
 
 	getNode := func(l *mdag.Link) (*mdag.Node, error) {
-		ctx, cancel := context.WithTimeout(context.TODO(), time.Minute)
-		defer cancel()
-
-		next, err := l.GetNode(ctx, t.opts.DAG)
+		next, err := l.GetNode(context.TODO(), t.opts.DAG)
 		if err != nil {
 			return nil, err
 		}

utils/utils.go

@@ -52,8 +52,7 @@ func addLink(ctx context.Context, ds dag.DAGService, root *dag.Node, childname s
 		return nil, err
 	}
 
-	_, err = ds.Add(root)
-	if err != nil {
+	if _, err := ds.Add(root); err != nil {
 		return nil, err
 	}
 	return root, nil