How is a file path formed in a Go application when working with "html/template" templates?

E

EmachinesDIMA2022-03-22 10:29:20

go

EmachinesDIMA, 2022-03-22 10:29:20

learning to write in Go.
I took this article as a basis https://habr.com/ru/post/475390/
but I pack it in docker.
I get the following error when compiling:

...
Recreating go-hello ... done
Attaching to go-hello
go-hello | panic: open index.html: no such file or directory
go-hello | 
go-hello | goroutine 1 [running]:
go-hello | html/template.Must(...)
go-hello |      /usr/local/go/src/html/template/template.go:374
go-hello | main.init()
go-hello |      /goapp/main.go:9 +0x8c
go-hello exited with code 2

what could be the reason for this problem? Searching the web didn't turn up any solutions.

application code

## ./app/main.go
---
package main
 
import (
    "html/template"
    "net/http"
    "os"
)
 
var tpl = template.Must(template.ParseFiles("index.html"))
 
func indexHandler(w http.ResponseWriter, r *http.Request) {
    // w.Write([]byte("<h1>Hello World!</h1>"))
    tpl.Execute(w, nil)
}
 
func main() {
    port := os.Getenv("PORT")
    if port == "" {
        port = "8080"
    }
 
    mux := http.NewServeMux()
 
    mux.HandleFunc("/", indexHandler)
    http.ListenAndServe(":"+port, mux)
}
 
---
---
---
## ./app/index.html
---
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>News App Demo</title>
    <link rel="stylesheet" href="/assets/style.css">
  </head>
 
  <body>
    <h1>News App Demo</h1>
  </body>
</html>
 
---
---
---
 
## ./Dockerfile
---
# syntax=docker/dockerfile:1
 
FROM golang:1.18-buster as builder
WORKDIR /goapp
COPY app/* ./
RUN go mod download
RUN  CGO_ENABLED=0  go build -o /hello-go
 
FROM alpine:3.14
WORKDIR /
COPY --from=builder /hello-go /hello-go
EXPOSE 8080
HEALTHCHECK --interval=5s --timeout=10s --retries=3 CMD curl -sS 127.0.0.1:8080 || exit 1
ENTRYPOINT ["/hello-go"]