CODE EXAMPLE FOR CSHARP

an existing connection was forcibly closed by the remote host. .net core

// If you face error while making inter service call in .net framework. (WEB API 2.0)
// user the below code before making an inter service call

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

// if want to use existing security protocols with new protocols
ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;