Fix typo in base64 example

examples/base64-encoding/base64-encoding.sh

@@ -1,7 +1,7 @@
 # The string encodes to slightly different values with the
 # standard and URL base64 encoders (trailing `+` vs `-`)
 # but they both decode to the original string as desired.
-$ go run base64-encoding.sh
+$ go run base64-encoding.go
 YWJjMTIzIT8kKiYoKSctPUB+
 abc123!?$*&()'-=@~