Simplify testing with TLS (#4095)

plugins/inputs/http/README.md

@@ -23,11 +23,11 @@ The HTTP input plugin collects metrics from one or more HTTP(S) endpoints.  The
   # username = "username"
   # password = "pa$$word"
 
-  ## Optional SSL Config
-  # ssl_ca = "/etc/telegraf/ca.pem"
-  # ssl_cert = "/etc/telegraf/cert.pem"
-  # ssl_key = "/etc/telegraf/key.pem"
-  ## Use SSL but skip chain & host verification
+  ## Optional TLS Config
+  # tls_ca = "/etc/telegraf/ca.pem"
+  # tls_cert = "/etc/telegraf/cert.pem"
+  # tls_key = "/etc/telegraf/key.pem"
+  ## Use TLS but skip chain & host verification
   # insecure_skip_verify = false
 
   ## Amount of time allowed to complete the HTTP request

plugins/inputs/http/http.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/internal/tls"
 	"github.com/influxdata/telegraf/plugins/inputs"
 	"github.com/influxdata/telegraf/plugins/parsers"
 )
@@ -24,15 +25,7 @@ type HTTP struct {
 	// HTTP Basic Auth Credentials
 	Username string
 	Password string
-
-	// Path to CA file
-	SSLCA string `toml:"ssl_ca"`
-	// Path to host cert file
-	SSLCert string `toml:"ssl_cert"`
-	// Path to cert key file
-	SSLKey string `toml:"ssl_key"`
-	// Use SSL but skip chain & host verification
-	InsecureSkipVerify bool
+	tls.ClientConfig
 
 	Timeout internal.Duration
 
@@ -62,11 +55,11 @@ var sampleConfig = `
   ## Tag all metrics with the url
   # tag_url = true
 
-  ## Optional SSL Config
-  # ssl_ca = "/etc/telegraf/ca.pem"
-  # ssl_cert = "/etc/telegraf/cert.pem"
-  # ssl_key = "/etc/telegraf/key.pem"
-  ## Use SSL but skip chain & host verification
+  ## Optional TLS Config
+  # tls_ca = "/etc/telegraf/ca.pem"
+  # tls_cert = "/etc/telegraf/cert.pem"
+  # tls_key = "/etc/telegraf/key.pem"
+  ## Use TLS but skip chain & host verification
   # insecure_skip_verify = false
 
   ## Amount of time allowed to complete the HTTP request
@@ -97,8 +90,7 @@ func (h *HTTP) Gather(acc telegraf.Accumulator) error {
 	}
 
 	if h.client == nil {
-		tlsCfg, err := internal.GetTLSConfig(
-			h.SSLCert, h.SSLKey, h.SSLCA, h.InsecureSkipVerify)
+		tlsCfg, err := h.ClientConfig.TLSConfig()
 		if err != nil {
 			return err
 		}