# E4037

Compiler diagnostic name: `pkg_not_imported`.

Cannot perform action: package is not imported.

Some language features require an explicit package import because the compiler
needs runtime support from that package. For example, `async fn main` and
`async test` require `moonbitlang/async`.

## Erroneous example

```{literalinclude} /sources/error_codes/4037_error/top.mbt
:language: moonbit
```

## Suggestion

Import the required package if you intend to use the feature. If you do not need
the feature, remove the construct that requires the package.

```{literalinclude} /sources/error_codes/4037_fixed/top.mbt
:language: moonbit
```