actix-web 4.0.0 got panic "there is no timer running, must be called from the context of Tokio runtime"

[SardineFish]

I'm working on a project with mongodb = 2.0.0-alpha and actix-web = 4.0.0-beta.1, both depends on tokio 1.x. But got panic when using mongodb :

there is no timer running, must be called from the context of Tokio runtime

I tried to roll back these crates to some old version that depends on tokio 0.2.x, it works.
Is it a bug or something I was missing with the new tokio version?

[robjtede]

Beta 3 is out and might fix your issue.