Now, instead of using independent `startup` and `shutdown` events, you can define that logic in a single function with `yield` decorated with `@asynccontextmanager` (an async context manager).

For example:

```Python
from contextlib import asynccontextmanager

padding-left: $gutter * .5;\n  margin-right: auto;\n  margin-left: auto;\n}\n\n@mixin make-row($gutter: $grid-gutter-width) {\n  display: flex;\n  flex-wrap: wrap;\n  margin-right: -$gutter * .5;\n  margin-left: -$gutter * .5;\n}\n\n// For each breakpoint, define the maximum width of the container in a media query\n@mixin make-container-max-widths($max-widths: $container-max-widths, $breakpoints: $grid-breakpoints) {\n  @each $breakpoint, $container-max-width in $max-widths {\n    @include media-breakpoint-up($breakpoint,...

pkg go/token, const CONST Token
pkg go/token, const CONTINUE Token
pkg go/token, const DEC Token
pkg go/token, const DEFAULT Token
pkg go/token, const DEFER Token
pkg go/token, const DEFINE Token
pkg go/token, const ELLIPSIS Token
pkg go/token, const ELSE Token
pkg go/token, const EOF Token
pkg go/token, const EQL Token
pkg go/token, const FALLTHROUGH Token
pkg go/token, const FLOAT Token

pkg go/token, const COMMENT = 2
pkg go/token, const CONST = 64
pkg go/token, const CONTINUE = 65
pkg go/token, const DEC = 38
pkg go/token, const DEFAULT = 66
pkg go/token, const DEFER = 67
pkg go/token, const DEFINE = 47
pkg go/token, const ELLIPSIS = 48
pkg go/token, const ELSE = 68
pkg go/token, const EOF = 1
pkg go/token, const EQL = 39
pkg go/token, const FALLTHROUGH = 69
pkg go/token, const FLOAT = 6

padding-left: $gutter * .5;\n  margin-right: auto;\n  margin-left: auto;\n}\n\n@mixin make-row($gutter: $grid-gutter-width) {\n  display: flex;\n  flex-wrap: wrap;\n  margin-right: -$gutter * .5;\n  margin-left: -$gutter * .5;\n}\n\n// For each breakpoint, define the maximum width of the container in a media query\n@mixin make-container-max-widths($max-widths: $container-max-widths, $breakpoints: $grid-breakpoints) {\n  @each $breakpoint, $container-max-width in $max-widths {\n    @include media-breakpoint-up($breakpoint,...