Upgraded to Gradle 6.6 and Kotlin 1.4.0.

src/main/kotlin/net/thauvin/erik/akismet/Akismet.kt

@@ -32,7 +32,6 @@
 package net.thauvin.erik.akismet
 
 import kotlinx.serialization.json.Json
-import kotlinx.serialization.json.JsonConfiguration
 import net.thauvin.erik.semver.Version
 import okhttp3.FormBody
 import okhttp3.HttpUrl
@@ -46,7 +45,7 @@ import java.time.OffsetDateTime
 import java.time.ZoneId
 import java.time.format.DateTimeFormatter
 import java.time.temporal.ChronoUnit
-import java.util.Date
+import java.util.*
 import java.util.logging.Level
 import java.util.logging.Logger
 
@@ -65,7 +64,7 @@ open class Akismet(apiKey: String) {
          */
         @JvmStatic
         fun jsonComment(json: String): AkismetComment {
-            return Json(JsonConfiguration.Stable).parse(AkismetComment.serializer(), json)
+            return Json.decodeFromString(AkismetComment.serializer(), json)
         }
 
         /**

src/main/kotlin/net/thauvin/erik/akismet/AkismetComment.kt

@@ -33,9 +33,14 @@
 package net.thauvin.erik.akismet
 
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
-import kotlinx.serialization.json.JsonConfiguration
 import javax.servlet.http.HttpServletRequest
+import kotlin.collections.HashMap
+import kotlin.collections.Map
+import kotlin.collections.emptyMap
+import kotlin.collections.iterator
+import kotlin.collections.set
 
 private fun String?.ifNull() = this ?: ""
 
@@ -259,7 +264,7 @@ open class AkismetComment(val userIp: String, val userAgent: String) {
      * @see [Akismet.jsonComment]
      */
     override fun toString(): String {
-        return Json(JsonConfiguration.Stable).stringify(serializer(), this)
+        return Json.encodeToString(this)
     }
 
     /**

src/test/kotlin/net/thauvin/erik/akismet/AkismetTest.kt

@@ -354,7 +354,7 @@ class AkismetTest {
 
     @Test
     fun jsonCommentTest() {
-        val jsonComment = Akismet.jsonComment(mockComment.toString())
+        val jsonComment = Akismet.jsonComment(mockComment.toJson())
 
         assertEquals(jsonComment, mockComment, "equals")
         assertEquals(jsonComment.hashCode(), mockComment.hashCode(), "hashcode")