org.gradle.internal.resolve.ArtifactResolveException: Could not download assertj-core-3.13.2.jar

Hi, I have been trying to import a Spring project in Intellij Idea, and I have added a Spring reactive dependency. 

This is my build.gradle file:

plugins {
   id 'org.springframework.boot' version '2.2.2.RELEASE'
   id 'io.spring.dependency-management' version '1.0.8.RELEASE'
   id 'java'
}

group = 'ReactiveTest'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
   mavenCentral()
}

dependencies {
   implementation 'org.springframework.boot:spring-boot-starter-webflux'
   testImplementation('org.springframework.boot:spring-boot-starter-test') {
      exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
   }
   testImplementation 'io.projectreactor:reactor-test'
}

test {
   useJUnitPlatform()
}

I get the following error:

Warning:<i><b>root project 'ReactiveTest': Unable to resolve additional project configuration.</b>
Details: org.gradle.api.artifacts.ResolveException: Could not resolve all dependencies for configuration ':testCompileClasspath'.
Caused by: org.gradle.internal.resolve.ArtifactResolveException: Could not download assertj-core-3.13.2.jar (org.assertj:assertj-core:3.13.2)
Caused by: org.gradle.api.resources.ResourceException: Could not get resource 'https://repo.maven.apache.org/maven2/org/assertj/assertj-core/3.13.2/assertj-core-3.13.2.jar'.
Caused by: org.gradle.internal.resource.transport.http.HttpRequestException: Could not GET 'https://repo.maven.apache.org/maven2/org/assertj/assertj-core/3.13.2/assertj-core-3.13.2.jar'.
Caused by: java.net.SocketTimeoutException: Read timed out</i>

If I remove this from build.gradle:

testImplementation('org.springframework.boot:spring-boot-starter-test') {
exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
}

The import is successful.

I can visit https://repo.maven.apache.org/maven2/org/assertj/assertj-core/3.13.2/assertj-core-3.13.2.jar manually using a browser. But it takes some time for the download to start.

I guess the time required for the download to initialize is what is causing the socket timeout exception.

How can I add this downloaded jar file manually in the build so IDEA does not have to download it externally?

Any help/workaround will be much appreciated.