NewGroup creates a Group.

NoTags can be passed to NewGroup as the tagName to indicate that the tracing spans created for operations should not have the operation key as a tag.

DoOpts groups options for the DoChan() method.

Future is the return type of the DoChan() call.

Group represents a class of work and forms a namespace in which units of work can be executed with duplicate suppression.

Result holds the results of Do, so they can be passed on a channel.