RCT: fix panic (#13502)

go.mod

@@ -197,3 +197,5 @@ require (
 )
 
 replace github.com/spf13/viper => github.com/spf13/viper v1.18.1
+
+replace github.com/mlnoga/rct => github.com/andig/rct v0.1.2-0.20240419102452-054695c3e7c2

go.sum

@@ -35,6 +35,8 @@ github.com/andig/gosunspec v0.0.0-20231205122018-1daccfa17912 h1:pphS+WUa9zK0ZH/
 github.com/andig/gosunspec v0.0.0-20231205122018-1daccfa17912/go.mod h1:c6P6szcR+ROkqZruOR4f6qbDKFjZX6OitPpj+yJ/r8k=
 github.com/andig/mbserver v0.0.0-20230310211055-1d29cbb5820e h1:m/NTP3JWpR7M0ljLxiQU4fzR25jjhe1LDtxLMNcoNJQ=
 github.com/andig/mbserver v0.0.0-20230310211055-1d29cbb5820e/go.mod h1:4VtYzTm//oUipwvO3yh0g/udTE7pYJM+U/kyAuFDsgM=
+github.com/andig/rct v0.1.2-0.20240419102452-054695c3e7c2 h1:hAQe9ESVfjlXi8NTyy+BnYtlIseP40GemlxTKmQCq4g=
+github.com/andig/rct v0.1.2-0.20240419102452-054695c3e7c2/go.mod h1:0lfd2mmBnBzIvuzYtdhG+2371u+cUfIxsYErm4P9KRI=
 github.com/andybalholm/cascadia v1.3.2 h1:3Xi6Dw5lHF15JtdcmAHD3i1+T8plmv7BQ/nsViSLyss=
 github.com/andybalholm/cascadia v1.3.2/go.mod h1:7gtRlve5FxPPgIgX36uWBX58OdBsSS6lUvCFb+h7KvU=
 github.com/apache/thrift v0.12.0/go.mod h1:cp2SuWMxlEZw2r+iP2GNCdIi4C1qmUzdZFSVb+bacwQ=
@@ -434,8 +436,6 @@ github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyua
 github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
 github.com/mitchellh/reflectwalk v1.0.2 h1:G2LzWKi524PWgd3mLHV8Y5k7s6XUvT0Gef6zxSIeXaQ=
 github.com/mitchellh/reflectwalk v1.0.2/go.mod h1:mSTlrgnPZtwu0c4WaC2kGObEpuNDbx0jmZXqmk4esnw=
-github.com/mlnoga/rct v0.1.2-0.20230731074838-03eacb926f99 h1:sX4VwA7zgImnMqRgEkzP+3oKCgUHRF0OvHghFJ0pntY=
-github.com/mlnoga/rct v0.1.2-0.20230731074838-03eacb926f99/go.mod h1:0lfd2mmBnBzIvuzYtdhG+2371u+cUfIxsYErm4P9KRI=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd h1:TRLaZ9cD/w8PVh93nsPXa1VrQ6jlwL5oN8l14QlcNfg=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=

meter/rct.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/cenkalti/backoff/v4"
@@ -74,8 +75,13 @@ func NewRCTFromConfig(other map[string]interface{}) (api.Meter, error) {
 	return NewRCT(cc.Uri, cc.Usage, cc.Cache, cc.capacity.Decorator())
 }
 
+var rctMu sync.Mutex
+
 // NewRCT creates an RCT meter
 func NewRCT(uri, usage string, cache time.Duration, capacity func() float64) (api.Meter, error) {
+	rctMu.Lock()
+	defer rctMu.Unlock()
+
 	conn, err := rct.NewConnection(uri, cache)
 	if err != nil {
 		return nil, err