Error : Could not get unknown property 'myAPIKey' for BuildType_Decorated

[koencirun]

Could not get unknown property 'myAPIKey' for BuildType_Decorated{name=debug, debuggable=true, testCoverageEnabled=false, jniDebuggable=false, pseudoLocalesEnabled=false, renderscriptDebuggable=false, renderscriptOptimLevel=3, minifyEnabled=false, zipAlignEnabled=true, signingConfig=SigningConfig_Decorated{name=debug, storeFile=C:\Users\Andriansyah.android\debug.keystore, storePassword=android, keyAlias=AndroidDebugKey, keyPassword=android, storeType=C:\Users\Andriansyah.android\debug.keystore, v1SigningEnabled=true, v2SigningEnabled=true}, embedMicroApp=false, mBuildConfigFields={}, mResValues={}, mProguardFiles=[], mConsumerProguardFiles=[], mManifestPlaceholders={}} of type com.android.build.gradle.internal.dsl.BuildType.

[koencirun]

what shoul i do?