Update Bucket.Get documentation

Signed-off-by: Cenk Alti <cenkalti@gmail.com>

bucket.go

@@ -248,6 +248,7 @@ func (b *Bucket) DeleteBucket(key []byte) error {
 // Get retrieves the value for a key in the bucket.
 // Returns a nil value if the key does not exist or if the key is a nested bucket.
 // The returned value is only valid for the life of the transaction.
+// The returned memory is owned by bbolt and must never be modified; writing to this memory might corrupt the database.
 func (b *Bucket) Get(key []byte) []byte {
 	k, v, flags := b.Cursor().seek(key)