rpc: remove NotifierContextKey

Context keys must have a unique type in order to prevent
any unintented clashes. The code used int(1) as key.

Fix it by implementing the pattern recommended by package context.

3 files changed, 4 insertions, 4 deletions

diff --git a/eth/api.go b/eth/api.go
index 41387c27f..a0b1f8ac2 100644
--- a/eth/api.go
+++ b/eth/api.go
@@ -603,7 +603,7 @@ type NewBlocksArgs struct {
 // NewBlocks triggers a new block event each time a block is appended to the chain. It accepts an argument which allows
 // the caller to specify whether the output should contain transactions and in what format.
 func (s *PublicBlockChainAPI) NewBlocks(ctx context.Context, args NewBlocksArgs) (rpc.Subscription, error) {
-	notifier, supported := ctx.Value(rpc.NotifierContextKey).(rpc.Notifier)
+	notifier, supported := rpc.NotifierFromContext(ctx)
 	if !supported {
 		return nil, rpc.ErrNotificationsUnsupported
 	}
@@ -1345,7 +1345,7 @@ func (s *PublicTransactionPoolAPI) PendingTransactions() []*RPCTransaction {
 // NewPendingTransaction creates a subscription that is triggered each time a transaction enters the transaction pool
 // and is send from one of the transactions this nodes manages.
 func (s *PublicTransactionPoolAPI) NewPendingTransactions(ctx context.Context) (rpc.Subscription, error) {
-	notifier, supported := ctx.Value(rpc.NotifierContextKey).(rpc.Notifier)
+	notifier, supported := rpc.NotifierFromContext(ctx)
 	if !supported {
 		return nil, rpc.ErrNotificationsUnsupported
 	}
diff --git a/eth/downloader/api.go b/eth/downloader/api.go
index 670a3ade3..94cd6515f 100644
--- a/eth/downloader/api.go
+++ b/eth/downloader/api.go
@@ -85,7 +85,7 @@ type SyncingResult struct {
 
 // Syncing provides information when this nodes starts synchronising with the Ethereum network and when it's finished.
 func (api *PublicDownloaderAPI) Syncing(ctx context.Context) (rpc.Subscription, error) {
-	notifier, supported := ctx.Value(rpc.NotifierContextKey).(rpc.Notifier)
+	notifier, supported := rpc.NotifierFromContext(ctx)
 	if !supported {
 		return nil, rpc.ErrNotificationsUnsupported
 	}
diff --git a/eth/filters/api.go b/eth/filters/api.go
index 9e95ebd83..d9bd4d4b7 100644
--- a/eth/filters/api.go
+++ b/eth/filters/api.go
@@ -234,7 +234,7 @@ func (s *PublicFilterAPI) newLogFilter(earliest, latest int64, addresses []commo
 }
 
 func (s *PublicFilterAPI) Logs(ctx context.Context, args NewFilterArgs) (rpc.Subscription, error) {
-	notifier, supported := ctx.Value(rpc.NotifierContextKey).(rpc.Notifier)
+	notifier, supported := rpc.NotifierFromContext(ctx)
 	if !supported {
 		return nil, rpc.ErrNotificationsUnsupported
 	}