What version of Hugo are you using: hugo v0.109.0-47b12b83e636224e5e601813ff3e6790c191e371+extended windows/amd64 BuildDate=2022-12-23T10:38:11Z VendorInfo=gohugoio
Does this issue reproduce with the latest release : Yes

Hello,
I’m currently doing some work that requires me to change the user agent of the client used for resources.GetRemote

Unfortunately, it seems that I'm unable to modify the User-Agent header, consider the following example:

{{ $opts := dict
    "method" "get"
    "headers" (dict
        "Authorization" "test-header"
        "User-Agent" "Mozilla/5.0" 
    )
}}
{{ with resources.GetRemote "https://127.0.0.1:8000" $opts }}
    {{ . }}
{{ end }}

The server sees:

GET / HTTP/1.1
Host: 127.0.0.1:8000
User-Agent: Hugo Static Site Generator
Authorization: test-header
Accept-Encoding: gzip

From what I can read in remote.go#L98 it seems that addDefaultHeaders is call first which sets the User-Agent header to Hugo Static Site Generator and then, addUserProvidedHeaders is called.

This functions uses req.Header.Add to add the header. The issue is that .Add does not override an existing header. Wouldn't it be preferable to use .Set which according to the documentation replaces any existing values associated with key?

Samuel,