feat: add server-sent events client #658 (#931)

Author: jeevatkm

client.go

@@ -58,6 +58,7 @@ var (
 	ErrUnsupportedRequestBodyKind = errors.New("resty: unsupported request body kind")
 
 	hdrUserAgentKey       = http.CanonicalHeaderKey("User-Agent")
+	hdrAcceptKey          = http.CanonicalHeaderKey("Accept")
 	hdrAcceptEncodingKey  = http.CanonicalHeaderKey("Accept-Encoding")
 	hdrContentTypeKey     = http.CanonicalHeaderKey("Content-Type")
 	hdrContentLengthKey   = http.CanonicalHeaderKey("Content-Length")

resty_test.go

@@ -34,7 +34,6 @@ import (
 
 var (
 	hdrLocationKey = http.CanonicalHeaderKey("Location")
-	hdrAcceptKey   = http.CanonicalHeaderKey("Accept")
 )
 
 //‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾

retry.go

@@ -115,7 +115,10 @@ func (b *backoffWithJitter) NextWaitDuration(c *Client, res *Response, err error
 		b.max = maxInt
 	}
 
-	retryStrategyFunc := c.RetryStrategy()
+	var retryStrategyFunc RetryStrategyFunc
+	if c != nil {
+		retryStrategyFunc = c.RetryStrategy()
+	}
 	if res == nil || retryStrategyFunc == nil {
 		return b.balanceMinMax(b.defaultStrategy(attempt)), nil
 	}