Fix: observatory log & JSON config(#1211)

Co-authored-by: ihotte <ihotte@yeah.net>

app/observatory/observer.go

@@ -152,7 +152,7 @@ func (o *Observer) probe(outbound string) ProbeResult {
 		fullerr := newError("underlying connection failed").Base(errorCollectorForRequest.UnderlyingError())
 		fullerr = newError("with outbound handler report").Base(fullerr)
 		fullerr = newError("GET request failed:", err).Base(fullerr)
-		fullerr = newError("the outbound ", outbound, "is dead:").Base(fullerr)
+		fullerr = newError("the outbound ", outbound, " is dead:").Base(fullerr)
 		fullerr = fullerr.AtInfo()
 		fullerr.WriteToLog()
 		return ProbeResult{Alive: false, LastErrorReason: fullerr.Error()}

infra/conf/observatory.go

@@ -10,7 +10,7 @@ import (
 type ObservatoryConfig struct {
 	SubjectSelector []string          `json:"subjectSelector"`
 	ProbeURL        string            `json:"probeURL"`
-	ProbeInterval   duration.Duration `json:"ProbeInterval"`
+	ProbeInterval   duration.Duration `json:"probeInterval"`
 }
 
 func (o *ObservatoryConfig) Build() (proto.Message, error) {