feat(inputs.prometheus): add support for Custom header

plugins/inputs/prometheus/prometheus.go

@@ -14,7 +14,7 @@ import (
 	"strings"
 	"sync"
 	"time"
-
+    
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
 
@@ -57,6 +57,8 @@ type Prometheus struct {
 	// Basic authentication credentials
 	Username string `toml:"username"`
 	Password string `toml:"password"`
+
+	HTTPHeaders map[string]string `toml:"http_headers"`
 
 	ResponseTimeout config.Duration `toml:"response_timeout"`
 
@@ -296,6 +298,12 @@ func (p *Prometheus) gatherURL(u URLAndAddress, acc telegraf.Accumulator) error
 		req.Header.Set("Authorization", "Bearer "+p.BearerTokenString)
 	} else if p.Username != "" || p.Password != "" {
 		req.SetBasicAuth(p.Username, p.Password)
+	} 
+
+	if p.HTTPHeaders != nil {
+		for key, value := range p.HTTPHeaders {
+ 		    req.Header.Add(key, value)                  
+		}
 	}
 
 	var resp *http.Response

plugins/inputs/prometheus/sample.conf

@@ -81,6 +81,10 @@
   # username = ""
   # password = ""
 
+  ## Add custom headers to the HTTP request
+  # http_headers = [{"header1",  "value1" },{ "header2", "value2" }]
+
+
   ## Specify timeout duration for slower prometheus clients (default is 3s)
   # response_timeout = "3s"