Perform a task inside the current fiber as part of the group.
This function temporarily adds the current fiber to the group for the sake of performing a specific function.
Once that function is done, the fiber leaves the group again.
If the group is killed while inside this function, the function returns early and the return type has the member
completed set to false. If the function ran to completion, completed is set to true, and result is set to
the function's return value (if one exists).
If the fiber is already a member of the group when this function is called, the function is simply executed
normally.
Perform a task inside the current fiber as part of the group.
This function temporarily adds the current fiber to the group for the sake of performing a specific function. Once that function is done, the fiber leaves the group again.
If the group is killed while inside this function, the function returns early and the return type has the member completed set to false. If the function ran to completion, completed is set to true, and result is set to the function's return value (if one exists).
If the fiber is already a member of the group when this function is called, the function is simply executed normally.