how to enable log nginx error log code example

Example: nginx access log format

log_format main 'site="$server_name" server="$host" dest_port="$server_port" dest_ip="$server_addr" '
                   'src="$remote_addr" src_ip="$realip_remote_addr" user="$remote_user" '
                   'time_local="$time_local" protocol="$server_protocol" status="$status" '
                   'bytes_out="$body_bytes_sent" bytes_in="$upstream_response_length" '
                   'http_referer="$http_referer" http_user_agent="$http_user_agent" '
                   'nginx_version="$nginx_version" http_x_forwarded_for="$http_x_forwarded_for" '
                   'http_x_header="$http_x_header" uri_query="$query_string" uri_path="$uri" '
                   'http_method="$request_method" response_time="$upstream_response_time" '
                   'cookie="$http_cookie" request_time="$request_time" ';