Unable to install esp8266 board in Arduino ide

[Albin1602]

Error downloading https://downloads.arduino.cc/packages/package_index.json
 Error downloading https://github.com/esp8266/Arduino/releases/download/2.7.1/esp8266-2.7.1.zip
java.lang.RuntimeException: java.lang.Exception: Error downloading https://github.com/esp8266/Arduino/releases/download/2.7.1/esp8266-2.7.1.zip
  at cc.arduino.contributions.packages.ui.ContributionManagerUI.lambda$onInstallPressed$2(ContributionManagerUI.java:175)
  at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.Exception: Error downloading https://github.com/esp8266/Arduino/releases/download/2.7.1/esp8266-2.7.1.zip
  at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:149)
  at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:83)
  at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:60)
  at cc.arduino.contributions.packages.ContributionInstaller.install(ContributionInstaller.java:105)
  at cc.arduino.contributions.packages.ui.ContributionManagerUI.lambda$onInstallPressed$2(ContributionManagerUI.java:172)
  ... 1 more
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
  at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1946)
  at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:316)
  at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:310)
  at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1639)
  at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:223)
  at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1037)
  at sun.security.ssl.Handshaker.process_record(Handshaker.java:965)
  at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1064)
  at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1367)
  at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1395)
  at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1379)
  at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:559)
  at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:185)
  at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162)
  at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150)
  at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:106)
  at cc.arduino.utils.network.FileDownloader.openConnectionAndFillTheFile(FileDownloader.java:234)
  at cc.arduino.utils.network.FileDownloader.downloadFile(FileDownloader.java:182)
  at cc.arduino.utils.network.FileDownloader.download(FileDownloader.java:129)
  at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:147)
  ... 5 more
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:397)
  at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:302)
  at sun.security.validator.Validator.validate(Validator.java:262)
  at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:324)
  at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)
  at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:124)
  at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1621)
  ... 21 more