error: future cannot be sent between threads safely when trying to build for wasm32-unknown-unknown

[setoelkahfi]

I'm trying to include a crate successfully built with uiffi-rs for Swift for wasm. I created a new crate called crate-networking-wasm and referenced the base crate_networking. When running wasm-pack build in the crate-networking-wasm I got this error:

error: future cannot be sent between threads safely
  --> /path-to-repo/lib/crate_networking/src/content.rs:17:1
   |
17 | #[export(async_runtime = "tokio")]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ future created by async block is not `Send`
   |

Any pointers?

Related:

• wasm-bindgen-futures stop working after upgrading uniffi-rs from v0.23 to v0.24 #1622
• unknown throw type error when composing multiple crate #2225

[badboy]

Hard to say without any code, so I can only guess:
one of your async functions in that block of code is holding things across waitpoints that are not Send and thus turn the whole future into not-Send.
You will have to restructure your code or wrap the parts into Send-able constructs.