Technically it seems mission impossible, but if materialized would be wonder in engineering world.China - Pakistan Railway, Kashgar - Gwadar Trains (travelchinaguide.com)
Two China - Pakistan Railways have been planned. In China, they will start from Kashgar Railway Station in the westernmost city of Kashgar of Xinjiang Uygur Autonomous Region. In Pakistan, both lines will be extended to the ports along Arabian Sea; one is the deep-sea Gwadar Port and the other is Karachi.
Kashgar - Gwadar Train: Kashgar- Gwadar Railway Project is planned to be built through the undeveloped north part of Pakistan, where no rail lines have been laid before. The Gwadar Port has been put into use on November 13, 2016, but the rail line is still at the planning stage and the aim is for it to be completed by 2030.
Kashgar - Karachi Train: They will run through the more prosperous cities in the east of the country, such as Islamabad, Peshawar, Lahore, and Karachi. A rail line has already existed between Karachi and Peshawar known as Pakistan First Railway Main Line. However, it needs to be renovated and upgraded. This work began in January, 2016 and is expected to be completed by 2019. In the future, the line will be extended to Kashgar. The whole line is a major part of China - Pakistan Economic Corridor and Silk Road Economic Belt.