Need help with configuring relay sentry setup with proxy

I want to connect relay to sentry.io via proxy service/application.
Please help me in this I am not able to find any way to put proxy between relay and sentry.

Config.yml

relay:
mode: managed
upstream: “https://sentry.io/
host: 0.0.0.0
port: 3000
tls_port: ~
tls_identity_path: ~
tls_identity_password: ~

Where I have to set the proxy in relay?