How to use arbitrary font in pgfplots?

I produce the following chart:

With the following code (compiled with XeLaTeX):

documentclass[border=5pt]{standalone}
usepackage[table]{xcolor} % more control over colors
usepackage{tikz}
usepackage{pgfplots}
usepackage{pgfplotstable}
usepackage{amsmath}
usepackage{amssymb}

% fonts
usepackage{mathspec}
setmainfont{[opensans.ttf]}

begin{document}

begin{tikzpicture}

pgfplotstableread[col sep=comma]{
country, 2Q20, 3Q20
US, 2, -1
Euro Area, 2, -2
UK, 2,-3
PR China, 2,-4
Korea, 2,-5
Chinese Taipei, 2,-6
Singapore, 2,-7
Indonesia, 2,-8
Philippines, 2,-9
Malaysia, 2,-10
}chart

begin{axis}[
font = footnotesize,
width = 10cm,
height = 6cm,
ybar,
bar width=2mm,
axis lines=left,
enlarge x limits=0.1,
enlarge y limits={.1, upper},
%
% y ticks style and label
ymin=-13,
ylabel={year-on-year change (%)},
ylabel shift = 1pt,
ytick distance = 5,
%
% x axis ticks and style
xtick=data,
xticklabels from table={chart}{country}, 
axis x line shift={pgfkeysvalueof{/pgfplots/ymin}},       
xticklabel shift={-pgfkeysvalueof{/pgfplots/axis x line shift}},
table/x expr = coordindex,                   
x tick label style = {rotate=90},]
%
% done with the axis, now the plots
addplot [black, fill, draw opacity = 0] table [y=2Q20]  {chart};
addplot [red, fill, draw opacity = 0, nodes near coords] table [y=3Q20]  {chart};
end{axis}
end{tikzpicture}

end{document}

As you can see, I am using fontspec to use Open Sans as my typeface (to download the opensans.ttf file I use, go to the Overleaf for this chart).

However, it applies only to the text, and not to the axis labels or nodes.

How can I use the otf/ttf file of my choice and have it apply to all those as well?

documentclass[border=5pt]{standalone}
usepackage[table]{xcolor} % more control over colors
usepackage{tikz}
usepackage{pgfplots}
usepackage{pgfplotstable}
usepackage{amsmath}
usepackage{amssymb}

% fonts
usepackage{mathspec}
setmainfont{Open Sans}
setmathsfont(Digits,Latin,Greek){Open Sans}

begin{document}

begin{tikzpicture}

pgfplotstableread[col sep=comma]{
country, 2Q20, 3Q20
US, 2, -1
Euro Area, 2, -2
UK, 2,-3
PR China, 2,-4
Korea, 2,-5
Chinese Taipei, 2,-6
Singapore, 2,-7
Indonesia, 2,-8
Philippines, 2,-9
Malaysia, 2,-10
}chart

begin{axis}[
font = footnotesize,
width = 10cm,
height = 6cm,
ybar,
bar width=2mm,
axis lines=left,
enlarge x limits=0.1,
enlarge y limits={.1, upper},
%
% y ticks style and label
ymin=-13,
ylabel={year-on-year change (%)},
ylabel shift = 1pt,
ytick distance = 5,
%
% x axis ticks and style
xtick=data,
xticklabels from table={chart}{country}, 
axis x line shift={pgfkeysvalueof{/pgfplots/ymin}},       
xticklabel shift={-pgfkeysvalueof{/pgfplots/axis x line shift}},
table/x expr = coordindex,                   
x tick label style = {rotate=90},]
%
% done with the axis, now the plots
addplot [black, fill, draw opacity = 0] table [y=2Q20]  {chart};
addplot [red, fill, draw opacity = 0, nodes near coords] table [y=3Q20]  {chart};
end{axis}
end{tikzpicture}

end{document}