E0156: A Go script with no end tag
A .vuka.html file's Go is the content of its <script lang="go">, up to the </script> that ends it. The compiler reads the Go as Go, so a </script> inside a string or a comment doesn't end it; the file has no other one, and the Go runs to the end of the file.
Wrong
html
<!-- counter.vuka.html -->
<script lang="go">
package components
type Counter struct{ n int }
func (c *Counter) Add() { c.n++ }
<button onClick={Add}>{n}</button>Right
html
<!-- counter.vuka.html -->
<script lang="go">
package components
type Counter struct{ n int }
func (c *Counter) Add() { c.n++ }
</script>
<button onClick={Add}>{n}</button>