https://ncbiinsights.ncbi.nlm.nih.gov/2018/03/20/stream-bam-files-custom-tracks-gdv-update/

We know it's important to you to be able to browse and visually inspect variants and alignments from your next-gen sequencing experiments, so we've added remote streaming of BAM files to the Genome Data Viewer (GDV). All you need are your BAM files and the index files (.bai extension) in a location that allows HTTP access and you can stream BAM files as custom tracks into the GDV.