Golang - Nginx proxy pass issue

I have a golang application running on port 3001.
curl http://127.0.0.1:3001 gives the correct HTML response. But I am facing issues when I am trying to do a proxy_pass via NginX.

Below is my NginX configuration. I am doing a route based location block –

upstream my-app {
    server 127.0.0.1:3001;
}

 server {
        listen       80 default_server;
        server_name  localhost;
        underscores_in_headers on;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        error_page 404 /404.html;
        client_max_body_size 300M;

            location ^~ /theapp {               
                proxy_redirect   off;
                proxy_set_header Host              $http_host;
                proxy_set_header X-Real-IP         $remote_addr;
                proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
                proxy_set_header X-Forwarded-Proto $scheme;

                proxy_pass       http://my-app;
            }
 }

When I access http://example.com/theapp/, it downloads the my-app binary instead of forwarding the http request to my-app.

What am I doing wrong?

Output of nginx -T –

nginx: the configuration file /mnt/vol1/nginx/conf/nginx.conf syntax is ok
nginx: configuration file /mnt/vol1/nginx/conf/nginx.conf test is successful
# configuration file /mnt/vol1/nginx/conf/nginx.conf:
#user  nobody;
worker_processes  12;

access_log  /mnt/vol2/logs/nginx/access.log  main-2 buffer=5k;
error_log   /mnt/vol2/logs/nginx/error.log;

events {
    worker_connections  4000;
     multi_accept        on;
}


http {
    include       mime.types;
    underscores_in_headers on;
    default_type  application/octet-stream;


    log_format  main-2 '$host $http_client_ip $remote_addr - $remote_user - $request_time [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for" '
                      '"$http_cache_control" '
                      '"$http_via" ';


    client_body_timeout 10;
    client_header_timeout 10;
    keepalive_timeout 5;
    send_timeout 10;
    sendfile        on;
      
    upstream my-app {
        server 127.0.0.1:3001;
    }

    server {
            listen       80 default_server;
            server_name  localhost;
            underscores_in_headers on;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            error_page 404 /404.html;
            client_max_body_size 300M;

                location ^~ /theapp {               
                    proxy_redirect   off;
                    proxy_set_header Host              $http_host;
                    proxy_set_header X-Real-IP         $remote_addr;
                    proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
                    proxy_set_header X-Forwarded-Proto $scheme;

                    proxy_pass       http://my-app;
                }
    }


} 

# configuration file /mnt/vol1/nginx/conf/mime.types:

types {
    text/html                             html htm shtml;
    text/css                              css;
    text/xml                              xml;
    image/gif                             gif;
    image/jpeg                            jpeg jpg;
    application/javascript                js;
    application/atom+xml                  atom;
    application/rss+xml                   rss;

    text/mathml                           mml;
    text/plain                            txt;
    text/vnd.sun.j2me.app-descriptor      jad;
    text/vnd.wap.wml                      wml;
    text/x-component                      htc;

    image/png                             png;
    image/tiff                            tif tiff;
    image/vnd.wap.wbmp                    wbmp;
    image/x-icon                          ico;
    image/x-jng                           jng;
    image/x-ms-bmp                        bmp;
    image/svg+xml                         svg svgz;
    image/webp                            webp;

    application/font-woff                 woff;
    application/java-archive              jar war ear;
    application/json                      json;
    application/mac-binhex40              hqx;
    application/msword                    doc;
    application/pdf                       pdf;
    application/postscript                ps eps ai;
    application/rtf                       rtf;
    application/vnd.apple.mpegurl         m3u8;
    application/vnd.ms-excel              xls;
    application/vnd.ms-fontobject         eot;
    application/vnd.ms-powerpoint         ppt;
    application/vnd.wap.wmlc              wmlc;
    application/vnd.google-earth.kml+xml  kml;
    application/vnd.google-earth.kmz      kmz;
    application/x-7z-compressed           7z;
    application/x-cocoa                   cco;
    application/x-java-archive-diff       jardiff;
    application/x-java-jnlp-file          jnlp;
    application/x-makeself                run;
    application/x-perl                    pl pm;
    application/x-pilot                   prc pdb;
    application/x-rar-compressed          rar;
    application/x-redhat-package-manager  rpm;
    application/x-sea                     sea;
    application/x-shockwave-flash         swf;
    application/x-stuffit                 sit;
    application/x-tcl                     tcl tk;
    application/x-x509-ca-cert            der pem crt;
    application/x-xpinstall               xpi;
    application/xhtml+xml                 xhtml;
    application/xspf+xml                  xspf;
    application/zip                       zip;

    application/octet-stream              bin exe dll;
    application/octet-stream              deb;
    application/octet-stream              dmg;
    application/octet-stream              iso img;
    application/octet-stream              msi msp msm;

    application/vnd.openxmlformats-officedocument.wordprocessingml.document    docx;
    application/vnd.openxmlformats-officedocument.spreadsheetml.sheet          xlsx;
    application/vnd.openxmlformats-officedocument.presentationml.presentation  pptx;

    audio/midi                            mid midi kar;
    audio/mpeg                            mp3;
    audio/ogg                             ogg;
    audio/x-m4a                           m4a;
    audio/x-realaudio                     ra;

    video/3gpp                            3gpp 3gp;
    video/mp2t                            ts;
    video/mp4                             mp4;
    video/mpeg                            mpeg mpg;
    video/quicktime                       mov;
    video/webm                            webm;
    video/x-flv                           flv;
    video/x-m4v                           m4v;
    video/x-mng                           mng;
    video/x-ms-asf                        asx asf;
    video/x-ms-wmv                        wmv;
    video/x-msvideo                       avi;
}